We noticed a performance regression when moving hadoop workloads from
3.10 kernels to 4.0 and 4.6. This is accompanied by increased pageout
activity initiated by kswapd as well as frequent bursts of allocation
stalls and direct reclaim scans. Even lowering the dirty ratios to the
equivalent of less than 1% of memory would not eliminate the issue,
suggesting that dirty pages concentrate where the scanner is looking.
This can be traced back to recent efforts of thrash avoidance. Where
3.10 would not detect refaulting pages and continuously supply clean
cache to the inactive list, a thrashing workload on 4.0+ will detect and
activate refaulting pages right away, distilling used-once pages on the
inactive list much more effectively. This is by design, and it makes
sense for clean cache. But for the most part our workload's cache
faults are refaults and its use-once cache is from streaming writes. We
end up with most of the inactive list dirty, and we don't go after the
active cache as long as we have use-once pages around.
But waiting for writes to avoid reclaiming clean cache that *might*
refault is a bad trade-off. Even if the refaults happen, reads are
faster than writes. Before getting bogged down on writeback, reclaim
should first look at *all* cache in the system, even active cache.
To accomplish this, activate pages that are dirty or under writeback
when they reach the end of the inactive LRU. The pages are marked for
immediate reclaim, meaning they'll get moved back to the inactive LRU
tail as soon as they're written back and become reclaimable. But in the
meantime, by reducing the inactive list to only immediately reclaimable
pages, we allow the scanner to deactivate and refill the inactive list
with clean cache from the active list tail to guarantee forward
progress.
[hannes@cmpxchg.org: update comment]
Link: http://lkml.kernel.org/r/20170202191957.22872-8-hannes@cmpxchg.org
Link: http://lkml.kernel.org/r/20170123181641.23938-6-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The patch is to improve the scalability of the swap out/in via using
fine grained locks for the swap cache. In current kernel, one address
space will be used for each swap device. And in the common
configuration, the number of the swap device is very small (one is
typical). This causes the heavy lock contention on the radix tree of
the address space if multiple tasks swap out/in concurrently.
But in fact, there is no dependency between pages in the swap cache. So
that, we can split the one shared address space for each swap device
into several address spaces to reduce the lock contention. In the
patch, the shared address space is split into 64MB trunks. 64MB is
chosen to balance the memory space usage and effect of lock contention
reduction.
The size of struct address_space on x86_64 architecture is 408B, so with
the patch, 6528B more memory will be used for every 1GB swap space on
x86_64 architecture.
One address space is still shared for the swap entries in the same 64M
trunks. To avoid lock contention for the first round of swap space
allocation, the order of the swap clusters in the initial free clusters
list is changed. The swap space distance between the consecutive swap
clusters in the free cluster list is at least 64M. After the first
round of allocation, the swap clusters are expected to be freed
randomly, so the lock contention should be reduced effectively.
Link: http://lkml.kernel.org/r/735bab895e64c930581ffb0a05b661e01da82bc5.1484082593.git.tim.c.chen@linux.intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net> escreveu:
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a new page flag, PageWaiters, to indicate the page waitqueue has
tasks waiting. This can be tested rather than testing waitqueue_active
which requires another cacheline load.
This bit is always set when the page has tasks on page_waitqueue(page),
and is set and cleared under the waitqueue lock. It may be set when
there are no tasks on the waitqueue, which will cause a harmless extra
wakeup check that will clears the bit.
The generic bit-waitqueue infrastructure is no longer used for pages.
Instead, waitqueues are used directly with a custom key type. The
generic code was not flexible enough to have PageWaiters manipulation
under the waitqueue lock (which simplifies concurrency).
This improves the performance of page lock intensive microbenchmarks by
2-3%.
Putting two bits in the same word opens the opportunity to remove the
memory barrier between clearing the lock bit and testing the waiters
bit, after some work on the arch primitives (e.g., ensuring memory
operand widths match and cover both bits).
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Andrew Lutomirski <luto@kernel.org>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The global zero page is used to satisfy an anonymous read fault. If
THP(Transparent HugePage) is enabled then the global huge zero page is
used. The global huge zero page uses an atomic counter for reference
counting and is allocated/freed dynamically according to its counter
value.
CPU time spent on that counter will greatly increase if there are a lot
of processes doing anonymous read faults. This patch proposes a way to
reduce the access to the global counter so that the CPU load can be
reduced accordingly.
To do this, a new flag of the mm_struct is introduced:
MMF_USED_HUGE_ZERO_PAGE. With this flag, the process only need to touch
the global counter in two cases:
1 The first time it uses the global huge zero page;
2 The time when mm_user of its mm_struct reaches zero.
Note that right now, the huge zero page is eligible to be freed as soon
as its last use goes away. With this patch, the page will not be
eligible to be freed until the exit of the last process from which it
was ever used.
And with the use of mm_user, the kthread is not eligible to use huge
zero page either. Since no kthread is using huge zero page today, there
is no difference after applying this patch. But if that is not desired,
I can change it to when mm_count reaches zero.
Case used for test on Haswell EP:
usemem -n 72 --readonly -j 0x200000 100G
Which spawns 72 processes and each will mmap 100G anonymous space and
then do read only access to that space sequentially with a step of 2MB.
CPU cycles from perf report for base commit:
54.03% usemem [kernel.kallsyms] [k] get_huge_zero_page
CPU cycles from perf report for this commit:
0.11% usemem [kernel.kallsyms] [k] mm_get_huge_zero_page
Performance(throughput) of the workload for base commit: 1784430792
Performance(throughput) of the workload for this commit: 4726928591
164% increase.
Runtime of the workload for base commit: 707592 us
Runtime of the workload for this commit: 303970 us
50% drop.
Link: http://lkml.kernel.org/r/fe51a88f-446a-4622-1363-ad1282d71385@intel.com
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With node-lru, the locking is based on the pgdat. Previously it was
required that a pagevec drain released one zone lru_lock and acquired
another zone lru_lock on every zone change. Now, it's only necessary if
the node changes. The end-result is fewer lock release/acquires if the
pages are all on the same node but in different zones.
Link: http://lkml.kernel.org/r/1468588165-12461-4-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This moves the LRU lists from the zone to the node and related data such
as counters, tracing, congestion tracking and writeback tracking.
Unfortunately, due to reclaim and compaction retry logic, it is
necessary to account for the number of LRU pages on both zone and node
logic. Most reclaim logic is based on the node counters but the retry
logic uses the zone counters which do not distinguish inactive and
active sizes. It would be possible to leave the LRU counters on a
per-zone basis but it's a heavier calculation across multiple cache
lines that is much more frequent than the retry checks.
Other than the LRU counters, this is mostly a mechanical patch but note
that it introduces a number of anomalies. For example, the scans are
per-zone but using per-node counters. We also mark a node as congested
when a zone is congested. This causes weird problems that are fixed
later but is easier to review.
In the event that there is excessive overhead on 32-bit systems due to
the nodes being on LRU then there are two potential solutions
1. Long-term isolation of highmem pages when reclaim is lowmem
When pages are skipped, they are immediately added back onto the LRU
list. If lowmem reclaim persisted for long periods of time, the same
highmem pages get continually scanned. The idea would be that lowmem
keeps those pages on a separate list until a reclaim for highmem pages
arrives that splices the highmem pages back onto the LRU. It potentially
could be implemented similar to the UNEVICTABLE list.
That would reduce the skip rate with the potential corner case is that
highmem pages have to be scanned and reclaimed to free lowmem slab pages.
2. Linear scan lowmem pages if the initial LRU shrink fails
This will break LRU ordering but may be preferable and faster during
memory pressure than skipping LRU pages.
Link: http://lkml.kernel.org/r/1467970510-21195-4-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Node-based reclaim requires node-based LRUs and locking. This is a
preparation patch that just moves the lru_lock to the node so later
patches are easier to review. It is a mechanical change but note this
patch makes contention worse because the LRU lock is hotter and direct
reclaim and kswapd can contend on the same lock even when reclaiming
from different zones.
Link: http://lkml.kernel.org/r/1467970510-21195-3-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Here's basic implementation of huge pages support for shmem/tmpfs.
It's all pretty streight-forward:
- shmem_getpage() allcoates huge page if it can and try to inserd into
radix tree with shmem_add_to_page_cache();
- shmem_add_to_page_cache() puts the page onto radix-tree if there's
space for it;
- shmem_undo_range() removes huge pages, if it fully within range.
Partial truncate of huge pages zero out this part of THP.
This have visible effect on fallocate(FALLOC_FL_PUNCH_HOLE)
behaviour. As we don't really create hole in this case,
lseek(SEEK_HOLE) may have inconsistent results depending what
pages happened to be allocated.
- no need to change shmem_fault: core-mm will map an compound page as
huge if VMA is suitable;
Link: http://lkml.kernel.org/r/1466021202-61880-30-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently we can have compound pages held on per cpu pagevecs, which
leads to a lot of memory unavailable for reclaim when needed. In the
systems with hundreads of processors it can be GBs of memory.
On of the way of reproducing the problem is to not call munmap
explicitly on all mapped regions (i.e. after receiving SIGTERM). After
that some pages (with THP enabled also huge pages) may end up on
lru_add_pvec, example below.
void main() {
#pragma omp parallel
{
size_t size = 55 * 1000 * 1000; // smaller than MEM/CPUS
void *p = mmap(NULL, size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS , -1, 0);
if (p != MAP_FAILED)
memset(p, 0, size);
//munmap(p, size); // uncomment to make the problem go away
}
}
When we run it with THP enabled it will leave significant amount of
memory on lru_add_pvec. This memory will be not reclaimed if we hit
OOM, so when we run above program in a loop:
for i in `seq 100`; do ./a.out; done
many processes (95% in my case) will be killed by OOM.
The primary point of the LRU add cache is to save the zone lru_lock
contention with a hope that more pages will belong to the same zone and
so their addition can be batched. The huge page is already a form of
batched addition (it will add 512 worth of memory in one go) so skipping
the batching seems like a safer option when compared to a potential
excess in the caching which can be quite large and much harder to fix
because lru_add_drain_all is way to expensive and it is not really clear
what would be a good moment to call it.
Similarly we can reproduce the problem on lru_deactivate_pvec by adding:
madvise(p, size, MADV_FREE); after memset.
This patch flushes lru pvecs on compound page arrival making the problem
less severe - after applying it kill rate of above example drops to 0%,
due to reducing maximum amount of memory held on pvec from 28MB (with
THP) to 56kB per CPU.
Suggested-by: Michal Hocko <mhocko@suse.com>
Link: http://lkml.kernel.org/r/1466180198-18854-1-git-send-email-lukasz.odzioba@intel.com
Signed-off-by: Lukasz Odzioba <lukasz.odzioba@intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Ming Li <mingli199x@qq.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch is based on https://patchwork.ozlabs.org/patch/574623/.
Tejun submitted commit 23d11a58a9 ("workqueue: skip flush dependency
checks for legacy workqueues") for the legacy create*_workqueue()
interface.
But some workq created by alloc_workqueue still reports warning on
memory reclaim, e.g nvme_workq with flag WQ_MEM_RECLAIM set:
workqueue: WQ_MEM_RECLAIM nvme:nvme_reset_work is flushing !WQ_MEM_RECLAIM events:lru_add_drain_per_cpu
------------[ cut here ]------------
WARNING: CPU: 0 PID: 6 at SoC/linux/kernel/workqueue.c:2448 check_flush_dependency+0xb4/0x10c
...
check_flush_dependency+0xb4/0x10c
flush_work+0x54/0x140
lru_add_drain_all+0x138/0x188
migrate_prep+0xc/0x18
alloc_contig_range+0xf4/0x350
cma_alloc+0xec/0x1e4
dma_alloc_from_contiguous+0x38/0x40
__dma_alloc+0x74/0x25c
nvme_alloc_queue+0xcc/0x36c
nvme_reset_work+0x5c4/0xda8
process_one_work+0x128/0x2ec
worker_thread+0x58/0x434
kthread+0xd4/0xe8
ret_from_fork+0x10/0x50
That's because lru_add_drain_all() will schedule the drain work on
system_wq, whose flag is set to 0, !WQ_MEM_RECLAIM.
Introduce a dedicated WQ_MEM_RECLAIM workqueue to do
lru_add_drain_all(), aiding in getting memory freed.
Link: http://lkml.kernel.org/r/1464917521-9775-1-git-send-email-shhuiw@foxmail.com
Signed-off-by: Wang Sheng-Hui <shhuiw@foxmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Put the activate_page_pvecs definition next to those of the other
pagevecs, for clarity.
Signed-off-by: Ming Li <mingli199x@qq.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andrea has found[1] a race condition on MMU-gather based TLB flush vs
split_huge_page() or shrinker which frees huge zero under us (patch 1/2
and 2/2 respectively).
With new THP refcounting, we don't need patch 1/2: mmu_gather keeps the
page pinned until flush is complete and the pin prevents the page from
being split under us.
We still need patch 2/2. This is simplified version of Andrea's patch.
We don't need fancy encoding.
[1] http://lkml.kernel.org/r/1447938052-22165-1-git-send-email-aarcange@redhat.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mostly direct substitution with occasional adjustment or removing
outdated comments.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time
ago with promise that one day it will be possible to implement page
cache with bigger chunks than PAGE_SIZE.
This promise never materialized. And unlikely will.
We have many places where PAGE_CACHE_SIZE assumed to be equal to
PAGE_SIZE. And it's constant source of confusion on whether
PAGE_CACHE_* or PAGE_* constant should be used in a particular case,
especially on the border between fs and mm.
Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much
breakage to be doable.
Let's stop pretending that pages in page cache are special. They are
not.
The changes are pretty straight-forward:
- <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;
- <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;
- PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN};
- page_cache_get() -> get_page();
- page_cache_release() -> put_page();
This patch contains automated changes generated with coccinelle using
script below. For some reason, coccinelle doesn't patch header files.
I've called spatch for them manually.
The only adjustment after coccinelle is revert of changes to
PAGE_CAHCE_ALIGN definition: we are going to drop it later.
There are few places in the code where coccinelle didn't reach. I'll
fix them manually in a separate patch. Comments and documentation also
will be addressed with the separate patch.
virtual patch
@@
expression E;
@@
- E << (PAGE_CACHE_SHIFT - PAGE_SHIFT)
+ E
@@
expression E;
@@
- E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT)
+ E
@@
@@
- PAGE_CACHE_SHIFT
+ PAGE_SHIFT
@@
@@
- PAGE_CACHE_SIZE
+ PAGE_SIZE
@@
@@
- PAGE_CACHE_MASK
+ PAGE_MASK
@@
expression E;
@@
- PAGE_CACHE_ALIGN(E)
+ PAGE_ALIGN(E)
@@
expression E;
@@
- page_cache_get(E)
+ get_page(E)
@@
expression E;
@@
- page_cache_release(E)
+ put_page(E)
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A dax mapping establishes a pte with _PAGE_DEVMAP set when the driver
has established a devm_memremap_pages() mapping, i.e. when the pfn_t
return from ->direct_access() has PFN_DEV and PFN_MAP set. Later, when
encountering _PAGE_DEVMAP during a page table walk we lookup and pin a
struct dev_pagemap instance to keep the result of pfn_to_page() valid
until put_page().
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
MADV_FREE is a hint that it's okay to discard pages if there is memory
pressure and we use reclaimers(ie, kswapd and direct reclaim) to free
them so there is no value keeping them in the active anonymous LRU so
this patch moves them to inactive LRU list's head.
This means that MADV_FREE-ed pages which were living on the inactive
list are reclaimed first because they are more likely to be cold rather
than recently active pages.
An arguable issue for the approach would be whether we should put the
page to the head or tail of the inactive list. I chose head because the
kernel cannot make sure it's really cold or warm for every MADV_FREE
usecase but at least we know it's not *hot*, so landing of inactive head
would be a comprimise for various usecases.
This fixes suboptimal behavior of MADV_FREE when pages living on the
active list will sit there for a long time even under memory pressure
while the inactive list is reclaimed heavily. This basically breaks the
whole purpose of using MADV_FREE to help the system to free memory which
is might not be used.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: <yalin.wang2010@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen Gang <gang.chen.5i5j@gmail.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Helge Deller <deller@gmx.de>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Jason Evans <je@fb.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Mika Penttil <mika.penttila@nextfour.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Roland Dreier <roland@kernel.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Before THP refcounting rework, THP was not allowed to cross VMA
boundary. So, if we have THP and we split it, PG_mlocked can be safely
transferred to small pages.
With new THP refcounting and naive approach to mlocking we can end up
with this scenario:
1. we have a mlocked THP, which belong to one VM_LOCKED VMA.
2. the process does munlock() on the *part* of the THP:
- the VMA is split into two, one of them VM_LOCKED;
- huge PMD split into PTE table;
- THP is still mlocked;
3. split_huge_page():
- it transfers PG_mlocked to *all* small pages regrardless if it
blong to any VM_LOCKED VMA.
We probably could munlock() all small pages on split_huge_page(), but I
think we have accounting issue already on step two.
Instead of forbidding mlocked pages altogether, we just avoid mlocking
PTE-mapped THPs and munlock THPs on split_huge_pmd().
This means PTE-mapped THPs will be on normal lru lists and will be split
under memory pressure by vmscan. After the split vmscan will detect
unevictable small pages and mlock them.
With this approach we shouldn't hit situation like described above.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Tail page refcounting is utterly complicated and painful to support.
It uses ->_mapcount on tail pages to store how many times this page is
pinned. get_page() bumps ->_mapcount on tail page in addition to
->_count on head. This information is required by split_huge_page() to
be able to distribute pins from head of compound page to tails during
the split.
We will need ->_mapcount to account PTE mappings of subpages of the
compound page. We eliminate need in current meaning of ->_mapcount in
tail pages by forbidding split entirely if the page is pinned.
The only user of tail page refcounting is THP which is marked BROKEN for
now.
Let's drop all this mess. It makes get_page() and put_page() much
simpler.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Hugh has pointed that compound_head() call can be unsafe in some
context. There's one example:
CPU0 CPU1
isolate_migratepages_block()
page_count()
compound_head()
!!PageTail() == true
put_page()
tail->first_page = NULL
head = tail->first_page
alloc_pages(__GFP_COMP)
prep_compound_page()
tail->first_page = head
__SetPageTail(p);
!!PageTail() == true
<head == NULL dereferencing>
The race is pure theoretical. I don't it's possible to trigger it in
practice. But who knows.
We can fix the race by changing how encode PageTail() and compound_head()
within struct page to be able to update them in one shot.
The patch introduces page->compound_head into third double word block in
front of compound_dtor and compound_order. Bit 0 encodes PageTail() and
the rest bits are pointer to head page if bit zero is set.
The patch moves page->pmd_huge_pte out of word, just in case if an
architecture defines pgtable_t into something what can have the bit 0
set.
hugetlb_cgroup uses page->lru.next in the second tail page to store
pointer struct hugetlb_cgroup. The patch switch it to use page->private
in the second tail page instead. The space is free since ->first_page is
removed from the union.
The patch also opens possibility to remove HUGETLB_CGROUP_MIN_ORDER
limitation, since there's now space in first tail page to store struct
hugetlb_cgroup pointer. But that's out of scope of the patch.
That means page->compound_head shares storage space with:
- page->lru.next;
- page->next;
- page->rcu_head.next;
That's too long list to be absolutely sure, but looks like nobody uses
bit 0 of the word.
page->rcu_head.next guaranteed[1] to have bit 0 clean as long as we use
call_rcu(), call_rcu_bh(), call_rcu_sched(), or call_srcu(). But future
call_rcu_lazy() is not allowed as it makes use of the bit and we can
get false positive PageTail().
[1] http://lkml.kernel.org/g/20150827163634.GD4029@linux.vnet.ibm.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Knowing the portion of memory that is not used by a certain application or
memory cgroup (idle memory) can be useful for partitioning the system
efficiently, e.g. by setting memory cgroup limits appropriately.
Currently, the only means to estimate the amount of idle memory provided
by the kernel is /proc/PID/{clear_refs,smaps}: the user can clear the
access bit for all pages mapped to a particular process by writing 1 to
clear_refs, wait for some time, and then count smaps:Referenced. However,
this method has two serious shortcomings:
- it does not count unmapped file pages
- it affects the reclaimer logic
To overcome these drawbacks, this patch introduces two new page flags,
Idle and Young, and a new sysfs file, /sys/kernel/mm/page_idle/bitmap.
A page's Idle flag can only be set from userspace by setting bit in
/sys/kernel/mm/page_idle/bitmap at the offset corresponding to the page,
and it is cleared whenever the page is accessed either through page tables
(it is cleared in page_referenced() in this case) or using the read(2)
system call (mark_page_accessed()). Thus by setting the Idle flag for
pages of a particular workload, which can be found e.g. by reading
/proc/PID/pagemap, waiting for some time to let the workload access its
working set, and then reading the bitmap file, one can estimate the amount
of pages that are not used by the workload.
The Young page flag is used to avoid interference with the memory
reclaimer. A page's Young flag is set whenever the Access bit of a page
table entry pointing to the page is cleared by writing to the bitmap file.
If page_referenced() is called on a Young page, it will add 1 to its
return value, therefore concealing the fact that the Access bit was
cleared.
Note, since there is no room for extra page flags on 32 bit, this feature
uses extended page flags when compiled on 32 bit.
[akpm@linux-foundation.org: fix build]
[akpm@linux-foundation.org: kpageidle requires an MMU]
[akpm@linux-foundation.org: decouple from page-flags rework]
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Greg Thelen <gthelen@google.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
My commit 8d63d99a5d ("mm: avoid tail page refcounting on non-THP
compound pages") which was merged during 4.1 merge window caused
regression:
page:ffffea0010a15040 count:0 mapcount:1 mapping: (null) index:0x0
flags: 0x8000000000008014(referenced|dirty|tail)
page dumped because: VM_BUG_ON_PAGE(page_mapcount(page) != 0)
------------[ cut here ]------------
kernel BUG at mm/swap.c:134!
The problem can be reproduced by playing *two* audio files at the same
time and then stopping one of players. I used two mplayers to trigger
this.
The VM_BUG_ON_PAGE() which triggers the bug is bogus:
Sound subsystem uses compound pages for its buffers, but unlike most
__GFP_COMP sound maps compound pages to userspace with PTEs.
In our case with two players map the buffer twice and therefore elevates
page_mapcount() on tail pages by two. When one of players exits it
unmaps the VMA and drops page_mapcount() to one and try to release
reference on the page with put_page().
My commit changes which path it takes under put_compound_page(). It hits
put_unrefcounted_compound_page() where VM_BUG_ON_PAGE() is. It sees
page_mapcount() == 1. The function wrongly assumes that subpages of
compound page cannot be be mapped by itself with PTEs..
The solution is simply drop the VM_BUG_ON_PAGE().
Note: there's no need to move the check under put_page_testzero().
Allocator will check the mapcount by itself before putting on free list.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: Borislav Petkov <bp@alien8.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__put_compound_page() calls __page_cache_release() to do some freeing
work, but it's obviously for thps, not for hugetlb. We don't care because
PageLRU is always cleared and page->mem_cgroup is always NULL for hugetlb.
But it's not correct and has potential risks, so let's make it
conditional.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Hugh Dickins <hughd@google.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
"deactivate_page" was created for file invalidation so it has too
specific logic for file-backed pages. So, let's change the name of the
function and date to a file-specific one and yield the generic name.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Wang, Yalin <Yalin.Wang@sonymobile.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull backing device changes from Jens Axboe:
"This contains a cleanup of how the backing device is handled, in
preparation for a rework of the life time rules. In this part, the
most important change is to split the unrelated nommu mmap flags from
it, but also removing a backing_dev_info pointer from the
address_space (and inode), and a cleanup of other various minor bits.
Christoph did all the work here, I just fixed an oops with pages that
have a swap backing. Arnd fixed a missing export, and Oleg killed the
lustre backing_dev_info from staging. Last patch was from Al,
unexporting parts that are now no longer needed outside"
* 'for-3.20/bdi' of git://git.kernel.dk/linux-block:
Make super_blocks and sb_lock static
mtd: export new mtd_mmap_capabilities
fs: make inode_to_bdi() handle NULL inode
staging/lustre/llite: get rid of backing_dev_info
fs: remove default_backing_dev_info
fs: don't reassign dirty inodes to default_backing_dev_info
nfs: don't call bdi_unregister
ceph: remove call to bdi_unregister
fs: remove mapping->backing_dev_info
fs: export inode_to_bdi and use it in favor of mapping->backing_dev_info
nilfs2: set up s_bdi like the generic mount_bdev code
block_dev: get bdev inode bdi directly from the block device
block_dev: only write bdev inode on close
fs: introduce f_op->mmap_capabilities for nommu mmap support
fs: kill BDI_CAP_SWAP_BACKED
fs: deduplicate noop_backing_dev_info
We don't create non-linear mappings anymore. Let's drop code which
handles them in rmap.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This bdi flag isn't too useful - we can determine that a vma is backed by
either swap or shmem trivially in the caller.
This also allows removing the backing_dev_info instaces for swap and shmem
in favor of noop_backing_dev_info.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
free_pages_and_swap_cache limits release_pages to PAGEVEC_SIZE chunks.
This is not a big deal for the normal release path but it completely kills
memcg uncharge batching which reduces res_counter spin_lock contention.
Dave has noticed this with his page fault scalability test case on a large
machine when the lock was basically dominating on all CPUs:
80.18% 80.18% [kernel] [k] _raw_spin_lock
|
--- _raw_spin_lock
|
|--66.59%-- res_counter_uncharge_until
| res_counter_uncharge
| uncharge_batch
| uncharge_list
| mem_cgroup_uncharge_list
| release_pages
| free_pages_and_swap_cache
| tlb_flush_mmu_free
| |
| |--90.12%-- unmap_single_vma
| | unmap_vmas
| | unmap_region
| | do_munmap
| | vm_munmap
| | sys_munmap
| | system_call_fastpath
| | __GI___munmap
| |
| --9.88%-- tlb_flush_mmu
| tlb_finish_mmu
| unmap_region
| do_munmap
| vm_munmap
| sys_munmap
| system_call_fastpath
| __GI___munmap
In his case the load was running in the root memcg and that part has been
handled by reverting 05b8430123 ("mm: memcontrol: use root_mem_cgroup
res_counter") because this is a clear regression, but the problem remains
inside dedicated memcgs.
There is no reason to limit release_pages to PAGEVEC_SIZE batches other
than lru_lock held times. This logic, however, can be moved inside the
function. mem_cgroup_uncharge_list and free_hot_cold_page_list do not
hold any lock for the whole pages_to_free list so it is safe to call them
in a single run.
The release_pages() code was previously breaking the lru_lock each
PAGEVEC_SIZE pages (ie, 14 pages). However this code has no usage of
pagevecs so switch to breaking the lock at least every SWAP_CLUSTER_MAX
(32) pages. This means that the lock acquisition frequency is
approximately halved and the max hold times are approximately doubled.
The now unneeded batching is removed from free_pages_and_swap_cache().
Also update the grossly out-of-date release_pages documentation.
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Dave Hansen <dave@sr71.net>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pages are now uncharged at release time, and all sources of batched
uncharges operate on lists of pages. Directly use those lists, and
get rid of the per-task batching state.
This also batches statistics accounting, in addition to the res
counter charges, to reduce IRQ-disabling and re-enabling.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The memcg uncharging code that is involved towards the end of a page's
lifetime - truncation, reclaim, swapout, migration - is impressively
complicated and fragile.
Because anonymous and file pages were always charged before they had their
page->mapping established, uncharges had to happen when the page type
could still be known from the context; as in unmap for anonymous, page
cache removal for file and shmem pages, and swap cache truncation for swap
pages. However, these operations happen well before the page is actually
freed, and so a lot of synchronization is necessary:
- Charging, uncharging, page migration, and charge migration all need
to take a per-page bit spinlock as they could race with uncharging.
- Swap cache truncation happens during both swap-in and swap-out, and
possibly repeatedly before the page is actually freed. This means
that the memcg swapout code is called from many contexts that make
no sense and it has to figure out the direction from page state to
make sure memory and memory+swap are always correctly charged.
- On page migration, the old page might be unmapped but then reused,
so memcg code has to prevent untimely uncharging in that case.
Because this code - which should be a simple charge transfer - is so
special-cased, it is not reusable for replace_page_cache().
But now that charged pages always have a page->mapping, introduce
mem_cgroup_uncharge(), which is called after the final put_page(), when we
know for sure that nobody is looking at the page anymore.
For page migration, introduce mem_cgroup_migrate(), which is called after
the migration is successful and the new page is fully rmapped. Because
the old page is no longer uncharged after migration, prevent double
charges by decoupling the page's memcg association (PCG_USED and
pc->mem_cgroup) from the page holding an actual charge. The new bits
PCG_MEM and PCG_MEMSW represent the respective charges and are transferred
to the new page during migration.
mem_cgroup_migrate() is suitable for replace_page_cache() as well,
which gets rid of mem_cgroup_replace_page_cache(). However, care
needs to be taken because both the source and the target page can
already be charged and on the LRU when fuse is splicing: grab the page
lock on the charge moving side to prevent changing pc->mem_cgroup of a
page under migration. Also, the lruvecs of both pages change as we
uncharge the old and charge the new during migration, and putback may
race with us, so grab the lru lock and isolate the pages iff on LRU to
prevent races and ensure the pages are on the right lruvec afterward.
Swap accounting is massively simplified: because the page is no longer
uncharged as early as swap cache deletion, a new mem_cgroup_swapout() can
transfer the page's memory+swap charge (PCG_MEMSW) to the swap entry
before the final put_page() in page reclaim.
Finally, page_cgroup changes are now protected by whatever protection the
page itself offers: anonymous pages are charged under the page table lock,
whereas page cache insertions, swapin, and migration hold the page lock.
Uncharging happens under full exclusion with no outstanding references.
Charging and uncharging also ensure that the page is off-LRU, which
serializes against charge migration. Remove the very costly page_cgroup
lock and set pc->flags non-atomically.
[mhocko@suse.cz: mem_cgroup_charge_statistics needs preempt_disable]
[vdavydov@parallels.com: fix flags definition]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Tested-by: Jet Chen <jet.chen@intel.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Tested-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
These patches rework memcg charge lifetime to integrate more naturally
with the lifetime of user pages. This drastically simplifies the code and
reduces charging and uncharging overhead. The most expensive part of
charging and uncharging is the page_cgroup bit spinlock, which is removed
entirely after this series.
Here are the top-10 profile entries of a stress test that reads a 128G
sparse file on a freshly booted box, without even a dedicated cgroup (i.e.
executing in the root memcg). Before:
15.36% cat [kernel.kallsyms] [k] copy_user_generic_string
13.31% cat [kernel.kallsyms] [k] memset
11.48% cat [kernel.kallsyms] [k] do_mpage_readpage
4.23% cat [kernel.kallsyms] [k] get_page_from_freelist
2.38% cat [kernel.kallsyms] [k] put_page
2.32% cat [kernel.kallsyms] [k] __mem_cgroup_commit_charge
2.18% kswapd0 [kernel.kallsyms] [k] __mem_cgroup_uncharge_common
1.92% kswapd0 [kernel.kallsyms] [k] shrink_page_list
1.86% cat [kernel.kallsyms] [k] __radix_tree_lookup
1.62% cat [kernel.kallsyms] [k] __pagevec_lru_add_fn
After:
15.67% cat [kernel.kallsyms] [k] copy_user_generic_string
13.48% cat [kernel.kallsyms] [k] memset
11.42% cat [kernel.kallsyms] [k] do_mpage_readpage
3.98% cat [kernel.kallsyms] [k] get_page_from_freelist
2.46% cat [kernel.kallsyms] [k] put_page
2.13% kswapd0 [kernel.kallsyms] [k] shrink_page_list
1.88% cat [kernel.kallsyms] [k] __radix_tree_lookup
1.67% cat [kernel.kallsyms] [k] __pagevec_lru_add_fn
1.39% kswapd0 [kernel.kallsyms] [k] free_pcppages_bulk
1.30% cat [kernel.kallsyms] [k] kfree
As you can see, the memcg footprint has shrunk quite a bit.
text data bss dec hex filename
37970 9892 400 48262 bc86 mm/memcontrol.o.old
35239 9892 400 45531 b1db mm/memcontrol.o
This patch (of 4):
The memcg charge API charges pages before they are rmapped - i.e. have an
actual "type" - and so every callsite needs its own set of charge and
uncharge functions to know what type is being operated on. Worse,
uncharge has to happen from a context that is still type-specific, rather
than at the end of the page's lifetime with exclusive access, and so
requires a lot of synchronization.
Rewrite the charge API to provide a generic set of try_charge(),
commit_charge() and cancel_charge() transaction operations, much like
what's currently done for swap-in:
mem_cgroup_try_charge() attempts to reserve a charge, reclaiming
pages from the memcg if necessary.
mem_cgroup_commit_charge() commits the page to the charge once it
has a valid page->mapping and PageAnon() reliably tells the type.
mem_cgroup_cancel_charge() aborts the transaction.
This reduces the charge API and enables subsequent patches to
drastically simplify uncharging.
As pages need to be committed after rmap is established but before they
are added to the LRU, page_add_new_anon_rmap() must stop doing LRU
additions again. Revive lru_cache_add_active_or_unevictable().
[hughd@google.com: fix shmem_unuse]
[hughd@google.com: Add comments on the private use of -EAGAIN]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This was formerly the series "Improve sequential read throughput" which
noted some major differences in performance of tiobench since 3.0.
While there are a number of factors, two that dominated were the
introduction of the fair zone allocation policy and changes to CFQ.
The behaviour of fair zone allocation policy makes more sense than
tiobench as a benchmark and CFQ defaults were not changed due to
insufficient benchmarking.
This series is what's left. It's one functional fix to the fair zone
allocation policy when used on NUMA machines and a reduction of overhead
in general. tiobench was used for the comparison despite its flaws as
an IO benchmark as in this case we are primarily interested in the
overhead of page allocator and page reclaim activity.
On UMA, it makes little difference to overhead
3.16.0-rc3 3.16.0-rc3
vanilla lowercost-v5
User 383.61 386.77
System 403.83 401.74
Elapsed 5411.50 5413.11
On a 4-socket NUMA machine it's a bit more noticable
3.16.0-rc3 3.16.0-rc3
vanilla lowercost-v5
User 746.94 802.00
System 65336.22 40852.33
Elapsed 27553.52 27368.46
This patch (of 6):
The LRU insertion and activate tracepoints take PFN as a parameter
forcing the overhead to the caller. Move the overhead to the tracepoint
fast-assign method to ensure the cost is only incurred when the
tracepoint is active.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Do we really need an exported alias for __SetPageReferenced()? Its
callers better know what they're doing, in which case the page would not
be already marked referenced. Kill init_page_accessed(), just
__SetPageReferenced() inline.
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Prabhakar Lad <prabhakar.csengg@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
aops->write_begin may allocate a new page and make it visible only to have
mark_page_accessed called almost immediately after. Once the page is
visible the atomic operations are necessary which is noticable overhead
when writing to an in-memory filesystem like tmpfs but should also be
noticable with fast storage. The objective of the patch is to initialse
the accessed information with non-atomic operations before the page is
visible.
The bulk of filesystems directly or indirectly use
grab_cache_page_write_begin or find_or_create_page for the initial
allocation of a page cache page. This patch adds an init_page_accessed()
helper which behaves like the first call to mark_page_accessed() but may
called before the page is visible and can be done non-atomically.
The primary APIs of concern in this care are the following and are used
by most filesystems.
find_get_page
find_lock_page
find_or_create_page
grab_cache_page_nowait
grab_cache_page_write_begin
All of them are very similar in detail to the patch creates a core helper
pagecache_get_page() which takes a flags parameter that affects its
behavior such as whether the page should be marked accessed or not. Then
old API is preserved but is basically a thin wrapper around this core
function.
Each of the filesystems are then updated to avoid calling
mark_page_accessed when it is known that the VM interfaces have already
done the job. There is a slight snag in that the timing of the
mark_page_accessed() has now changed so in rare cases it's possible a page
gets to the end of the LRU as PageReferenced where as previously it might
have been repromoted. This is expected to be rare but it's worth the
filesystem people thinking about it in case they see a problem with the
timing change. It is also the case that some filesystems may be marking
pages accessed that previously did not but it makes sense that filesystems
have consistent behaviour in this regard.
The test case used to evaulate this is a simple dd of a large file done
multiple times with the file deleted on each iterations. The size of the
file is 1/10th physical memory to avoid dirty page balancing. In the
async case it will be possible that the workload completes without even
hitting the disk and will have variable results but highlight the impact
of mark_page_accessed for async IO. The sync results are expected to be
more stable. The exception is tmpfs where the normal case is for the "IO"
to not hit the disk.
The test machine was single socket and UMA to avoid any scheduling or NUMA
artifacts. Throughput and wall times are presented for sync IO, only wall
times are shown for async as the granularity reported by dd and the
variability is unsuitable for comparison. As async results were variable
do to writback timings, I'm only reporting the maximum figures. The sync
results were stable enough to make the mean and stddev uninteresting.
The performance results are reported based on a run with no profiling.
Profile data is based on a separate run with oprofile running.
async dd
3.15.0-rc3 3.15.0-rc3
vanilla accessed-v2
ext3 Max elapsed 13.9900 ( 0.00%) 11.5900 ( 17.16%)
tmpfs Max elapsed 0.5100 ( 0.00%) 0.4900 ( 3.92%)
btrfs Max elapsed 12.8100 ( 0.00%) 12.7800 ( 0.23%)
ext4 Max elapsed 18.6000 ( 0.00%) 13.3400 ( 28.28%)
xfs Max elapsed 12.5600 ( 0.00%) 2.0900 ( 83.36%)
The XFS figure is a bit strange as it managed to avoid a worst case by
sheer luck but the average figures looked reasonable.
samples percentage
ext3 86107 0.9783 vmlinux-3.15.0-rc4-vanilla mark_page_accessed
ext3 23833 0.2710 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed
ext3 5036 0.0573 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed
ext4 64566 0.8961 vmlinux-3.15.0-rc4-vanilla mark_page_accessed
ext4 5322 0.0713 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed
ext4 2869 0.0384 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed
xfs 62126 1.7675 vmlinux-3.15.0-rc4-vanilla mark_page_accessed
xfs 1904 0.0554 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed
xfs 103 0.0030 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed
btrfs 10655 0.1338 vmlinux-3.15.0-rc4-vanilla mark_page_accessed
btrfs 2020 0.0273 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed
btrfs 587 0.0079 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed
tmpfs 59562 3.2628 vmlinux-3.15.0-rc4-vanilla mark_page_accessed
tmpfs 1210 0.0696 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed
tmpfs 94 0.0054 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed
[akpm@linux-foundation.org: don't run init_page_accessed() against an uninitialised pointer]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Tested-by: Prabhakar Lad <prabhakar.csengg@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When adding pages to the LRU we clear the active bit unconditionally.
As the page could be reachable from other paths we cannot use unlocked
operations without risk of corruption such as a parallel
mark_page_accessed. This patch tests if is necessary to clear the
active flag before using an atomic operation. This potentially opens a
tiny race when PageActive is checked as mark_page_accessed could be
called after PageActive was checked. The race already exists but this
patch changes it slightly. The consequence is that that the page may be
promoted to the active list that might have been left on the inactive
list before the patch. It's too tiny a race and too marginal a
consequence to always use atomic operations for.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There should be no references to it any more and a parallel mark should
not be reordered against us. Use non-locked varient to clear page active.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
cold is a bool, make it one. Make the likely case the "if" part of the
block instead of the else as according to the optimisation manual this is
preferred.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently, in put_compound_page(), we have
======
if (likely(!PageTail(page))) { <------ (1)
if (put_page_testzero(page)) {
/*
¦* By the time all refcounts have been released
¦* split_huge_page cannot run anymore from under us.
¦*/
if (PageHead(page))
__put_compound_page(page);
else
__put_single_page(page);
}
return;
}
/* __split_huge_page_refcount can run under us */
page_head = compound_head(page); <------------ (2)
======
if at (1) , we fail the check, this means page is *likely* a tail page.
Then at (2), as compoud_head(page) is inlined, it is :
======
static inline struct page *compound_head(struct page *page)
{
if (unlikely(PageTail(page))) { <----------- (3)
struct page *head = page->first_page;
smp_rmb();
if (likely(PageTail(page)))
return head;
}
return page;
}
======
here, the (3) unlikely in the case is a negative hint, because it is
*likely* a tail page. So the check (3) in this case is not good, so I
introduce a helper for this case.
So this patch introduces compound_head_by_tail() which deals with a
possible tail page(though it could be spilt by a racy thread), and make
compound_head() a wrapper on it.
This patch has no functional change, and it reduces the object
size slightly:
text data bss dec hex filename
11003 1328 16 12347 303b mm/swap.o.orig
10971 1328 16 12315 301b mm/swap.o.patched
I've ran "perf top -e branch-miss" to observe branch-miss in this case.
As Michael points out, it's a slow path, so only very few times this case
happens. But I grep'ed the code base, and found there still are some
other call sites could be benifited from this helper. And given that it
only bloating up the source by only 5 lines, but with a reduced object
size. I still believe this helper deserves to exsit.
Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Jiang Liu <liuj97@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently, put_compound_page() carefully handles tricky cases to avoid
racing with compound page releasing or splitting, which makes it quite
lenthy (about 200+ lines) and needs deep tab indention, which makes it
quite hard to follow and maintain.
Now based on two helpers introduced in the previous patch ("mm/swap.c:
introduce put_[un]refcounted_compound_page helpers for spliting
put_compound_page"), this patch replaces those two lengthy code paths with
these two helpers, respectively. Also, it has some comment rephrasing.
After this patch, the put_compound_page() is very compact, thus easy to
read and maintain.
After splitting, the object file is of same size as the original one.
Actually, I've diff'ed put_compound_page()'s orginal disassemble code and
the patched disassemble code, the are 100% the same!
This fact shows that this splitting has no functional change, but it
brings readability.
This patch and the previous one blow the code by 32 lines, mostly due to
comments.
Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Jiang Liu <liuj97@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently, put_compound_page() carefully handles tricky cases to avoid
racing with compound page releasing or splitting, which makes it quite
lenthy (about 200+ lines) and needs deep tab indention, which makes it
quite hard to follow and maintain.
This patch and the next patch refactor this function.
Based on the code skeleton of put_compound_page:
put_compound_pge:
if !PageTail(page)
put head page fastpath;
return;
/* else PageTail */
page_head = compound_head(page)
if !__compound_tail_refcounted(page_head)
put head page optimal path; <---(1)
return;
else
put head page slowpath; <--- (2)
return;
This patch introduces two helpers, put_[un]refcounted_compound_page,
handling the code path (1) and code path (2), respectively. They both are
tagged __always_inline, thus elmiating function call overhead, making them
operating the same way as before.
They are almost copied verbatim(except one place, a "goto out_put_single"
is expanded), with some comments rephrasing.
Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Jiang Liu <liuj97@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Replace places where __get_cpu_var() is used for an address calculation
with this_cpu_ptr().
Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In mm/swap.c, __lru_cache_add() is exported, but actually there are no
users outside this file.
This patch unexports __lru_cache_add(), and makes it static. It also
exports lru_cache_add_file(), as it is use by cifs and fuse, which can
loaded as modules.
Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Reviewed-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The VM maintains cached filesystem pages on two types of lists. One
list holds the pages recently faulted into the cache, the other list
holds pages that have been referenced repeatedly on that first list.
The idea is to prefer reclaiming young pages over those that have shown
to benefit from caching in the past. We call the recently usedbut
ultimately was not significantly better than a FIFO policy and still
thrashed cache based on eviction speed, rather than actual demand for
cache.
This patch solves one half of the problem by decoupling the ability to
detect working set changes from the inactive list size. By maintaining
a history of recently evicted file pages it can detect frequently used
pages with an arbitrarily small inactive list size, and subsequently
apply pressure on the active list based on actual demand for cache, not
just overall eviction speed.
Every zone maintains a counter that tracks inactive list aging speed.
When a page is evicted, a snapshot of this counter is stored in the
now-empty page cache radix tree slot. On refault, the minimum access
distance of the page can be assessed, to evaluate whether the page
should be part of the active list or not.
This fixes the VM's blindness towards working set changes in excess of
the inactive list. And it's the foundation to further improve the
protection ability and reduce the minimum inactive list size of 50%.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Metin Doslu <metin@citusdata.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ozgun Erdogan <ozgun@citusdata.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
shmem mappings already contain exceptional entries where swap slot
information is remembered.
To be able to store eviction information for regular page cache, prepare
every site dealing with the radix trees directly to handle entries other
than pages.
The common lookup functions will filter out non-page entries and return
NULL for page cache holes, just as before. But provide a raw version of
the API which returns non-page entries as well, and switch shmem over to
use it.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Metin Doslu <metin@citusdata.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ozgun Erdogan <ozgun@citusdata.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit bf6bddf192 ("mm: introduce compaction and migration for
ballooned pages") introduces page_count(page) into memory compaction
which dereferences page->first_page if PageTail(page).
This results in a very rare NULL pointer dereference on the
aforementioned page_count(page). Indeed, anything that does
compound_head(), including page_count() is susceptible to racing with
prep_compound_page() and seeing a NULL or dangling page->first_page
pointer.
This patch uses Andrea's implementation of compound_trans_head() that
deals with such a race and makes it the default compound_head()
implementation. This includes a read memory barrier that ensures that
if PageTail(head) is true that we return a head page that is neither
NULL nor dangling. The patch then adds a store memory barrier to
prep_compound_page() to ensure page->first_page is set.
This is the safest way to ensure we see the head page that we are
expecting, PageTail(page) is already in the unlikely() path and the
memory barriers are unfortunately required.
Hugetlbfs is the exception, we don't enforce a store memory barrier
during init since no race is possible.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Holger Kiehl <Holger.Kiehl@dwd.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Most of the VM_BUG_ON assertions are performed on a page. Usually, when
one of these assertions fails we'll get a BUG_ON with a call stack and
the registers.
I've recently noticed based on the requests to add a small piece of code
that dumps the page to various VM_BUG_ON sites that the page dump is
quite useful to people debugging issues in mm.
This patch adds a VM_BUG_ON_PAGE(cond, page) which beyond doing what
VM_BUG_ON() does, also dumps the page before executing the actual
BUG_ON.
[akpm@linux-foundation.org: fix up includes]
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Tweak it so save a tab stop, make code layout slightly less nutty.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Pravin Shelar <pshelar@nicira.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This skips the _mapcount mangling for slab and hugetlbfs pages.
The main trouble in doing this is to guarantee that PageSlab and
PageHeadHuge remains constant for all get_page/put_page run on the tail
of slab or hugetlbfs compound pages. Otherwise if they're set during
get_page but not set during put_page, the _mapcount of the tail page
would underflow.
PageHeadHuge will remain true until the compound page is released and
enters the buddy allocator so it won't risk to change even if the tail
page is the last reference left on the page.
PG_slab instead is cleared before the slab frees the head page with
put_page, so if the tail pin is released after the slab freed the page,
we would have a problem. But in the slab case the tail pin cannot be
the last reference left on the page. This is because the slab code is
free to reuse the compound page after a kfree/kmem_cache_free without
having to check if there's any tail pin left. In turn all tail pins
must be always released while the head is still pinned by the slab code
and so we know PG_slab will be still set too.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Pravin Shelar <pshelar@nicira.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We don't actually need a reference on the head page in the slab and
hugetlbfs paths, as long as we add a smp_rmb() which should be faster
than get_page_unless_zero.
[akpm@linux-foundation.org: fix typo in comment]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Pravin Shelar <pshelar@nicira.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 7cb2ef56e6 ("mm: fix aio performance regression for database
caused by THP") can cause dereference of a dangling pointer if
split_huge_page runs during PageHuge() if there are updates to the
tail_page->private field.
Also it is repeating compound_head twice for hugetlbfs and it is running
compound_head+compound_trans_head for THP when a single one is needed in
both cases.
The new code within the PageSlab() check doesn't need to verify that the
THP page size is never bigger than the smallest hugetlbfs page size, to
avoid memory corruption.
A longstanding theoretical race condition was found while fixing the
above (see the change right after the skip_unlock label, that is
relevant for the compound_lock path too).
By re-establishing the _mapcount tail refcounting for all compound
pages, this also fixes the below problem:
echo 0 >/sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
BUG: Bad page state in process bash pfn:59a01
page:ffffea000139b038 count:0 mapcount:10 mapping: (null) index:0x0
page flags: 0x1c00000000008000(tail)
Modules linked in:
CPU: 6 PID: 2018 Comm: bash Not tainted 3.12.0+ #25
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Call Trace:
dump_stack+0x55/0x76
bad_page+0xd5/0x130
free_pages_prepare+0x213/0x280
__free_pages+0x36/0x80
update_and_free_page+0xc1/0xd0
free_pool_huge_page+0xc2/0xe0
set_max_huge_pages.part.58+0x14c/0x220
nr_hugepages_store_common.isra.60+0xd0/0xf0
nr_hugepages_store+0x13/0x20
kobj_attr_store+0xf/0x20
sysfs_write_file+0x189/0x1e0
vfs_write+0xc5/0x1f0
SyS_write+0x55/0xb0
system_call_fastpath+0x16/0x1b
Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Tested-by: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Pravin Shelar <pshelar@nicira.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There were two places where return value from bdi_init was not tested.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
make lru_add_drain_all() only selectively interrupt the cpus that have
per-cpu free pages that can be drained.
This is important in nohz mode where calling mlockall(), for example,
otherwise will interrupt every core unnecessarily.
This is important on workloads where nohz cores are handling 10 Gb traffic
in userspace. Those CPUs do not enter the kernel and place pages into LRU
pagevecs and they really, really don't want to be interrupted, or they
drop packets on the floor.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Reviewed-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I am working with a tool that simulates oracle database I/O workload.
This tool (orion to be specific -
<http://docs.oracle.com/cd/E11882_01/server.112/e16638/iodesign.htm#autoId24>)
allocates hugetlbfs pages using shmget() with SHM_HUGETLB flag. It then
does aio into these pages from flash disks using various common block
sizes used by database. I am looking at performance with two of the most
common block sizes - 1M and 64K. aio performance with these two block
sizes plunged after Transparent HugePages was introduced in the kernel.
Here are performance numbers:
pre-THP 2.6.39 3.11-rc5
1M read 8384 MB/s 5629 MB/s 6501 MB/s
64K read 7867 MB/s 4576 MB/s 4251 MB/s
I have narrowed the performance impact down to the overheads introduced by
THP in __get_page_tail() and put_compound_page() routines. perf top shows
>40% of cycles being spent in these two routines. Every time direct I/O
to hugetlbfs pages starts, kernel calls get_page() to grab a reference to
the pages and calls put_page() when I/O completes to put the reference
away. THP introduced significant amount of locking overhead to get_page()
and put_page() when dealing with compound pages because hugepages can be
split underneath get_page() and put_page(). It added this overhead
irrespective of whether it is dealing with hugetlbfs pages or transparent
hugepages. This resulted in 20%-45% drop in aio performance when using
hugetlbfs pages.
Since hugetlbfs pages can not be split, there is no reason to go through
all the locking overhead for these pages from what I can see. I added
code to __get_page_tail() and put_compound_page() to bypass all the
locking code when working with hugetlbfs pages. This improved performance
significantly. Performance numbers with this patch:
pre-THP 3.11-rc5 3.11-rc5 + Patch
1M read 8384 MB/s 6501 MB/s 8371 MB/s
64K read 7867 MB/s 4251 MB/s 6510 MB/s
Performance with 64K read is still lower than what it was before THP, but
still a 53% improvement. It does mean there is more work to be done but I
will take a 53% improvement for now.
Please take a look at the following patch and let me know if it looks
reasonable.
[akpm@linux-foundation.org: tweak comments]
Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Pravin B Shelar <pshelar@nicira.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
active/inactive lru lists can contain unevicable pages (i.e. ramfs pages
that have been placed on the LRU lists when first allocated), but these
pages must not have PageUnevictable set - otherwise shrink_[in]active_list
goes crazy:
kernel BUG at /home/space/kas/git/public/linux-next/mm/vmscan.c:1122!
1090 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1091 struct lruvec *lruvec, struct list_head *dst,
1092 unsigned long *nr_scanned, struct scan_control *sc,
1093 isolate_mode_t mode, enum lru_list lru)
1094 {
...
1108 switch (__isolate_lru_page(page, mode)) {
1109 case 0:
...
1116 case -EBUSY:
...
1121 default:
1122 BUG();
1123 }
1124 }
...
1130 }
__isolate_lru_page() returns EINVAL for PageUnevictable(page).
For lru_add_page_tail(), it means we should not set PageUnevictable()
for tail pages unless we're sure that it will go to LRU_UNEVICTABLE.
Let's just copy PG_active and PG_unevictable from head page in
__split_huge_page_refcount(), it will simplify lru_add_page_tail().
This will fix one more bug in lru_add_page_tail(): if
page_evictable(page_tail) is false and PageLRU(page) is true, page_tail
will go to the same lru as page, but nobody cares to sync page_tail
active/inactive state with page. So we can end up with inactive page on
active lru. The patch will fix it as well since we copy PG_active from
head page.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
As a result of commit 13f7f78981 ("mm: pagevec: defer deciding which
LRU to add a page to until pagevec drain time"), pages on unevictable
lists can have both of PageActive and PageUnevictable set. This is not
only confusing, but also corrupts page migration and
shrink_[in]active_list.
This patch fixes the problem by adding ClearPageActive before adding
pages into unevictable list. It also cleans up VM_BUG_ONs.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Similar to __pagevec_lru_add, this patch removes the LRU parameter from
__lru_cache_add and lru_cache_add_lru as the caller does not control the
exact LRU the page gets added to. lru_cache_add_lru gets renamed to
lru_cache_add the name is silly without the lru parameter. With the
parameter removed, it is required that the caller indicate if they want
the page added to the active or inactive list by setting or clearing
PageActive respectively.
[akpm@linux-foundation.org: Suggested the patch]
[gang.chen@asianux.com: fix used-unintialized warning]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alexey Lyahkov <alexey.lyashkov@gmail.com>
Cc: Andrew Perepechko <anserper@ya.ru>
Cc: Robin Dong <sanbai@taobao.com>
Cc: Theodore Tso <tytso@mit.edu>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Bernd Schubert <bernd.schubert@fastmail.fm>
Cc: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now that the LRU to add a page to is decided at LRU-add time, remove the
misleading lru parameter from __pagevec_lru_add. A consequence of this
is that the pagevec_lru_add_file, pagevec_lru_add_anon and similar
helpers are misleading as the caller no longer has direct control over
what LRU the page is added to. Unused helpers are removed by this patch
and existing users of pagevec_lru_add_file() are converted to use
lru_cache_add_file() directly and use the per-cpu pagevecs instead of
creating their own pagevec.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alexey Lyahkov <alexey.lyashkov@gmail.com>
Cc: Andrew Perepechko <anserper@ya.ru>
Cc: Robin Dong <sanbai@taobao.com>
Cc: Theodore Tso <tytso@mit.edu>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Bernd Schubert <bernd.schubert@fastmail.fm>
Cc: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If a page is on a pagevec then it is !PageLRU and mark_page_accessed()
may fail to move a page to the active list as expected. Now that the
LRU is selected at LRU drain time, mark pages PageActive if they are on
the local pagevec so it gets moved to the correct list at LRU drain
time. Using a debugging patch it was found that for a simple git
checkout based workload that pages were never added to the active file
list in practice but with this patch applied they are.
before after
LRU Add Active File 0 750583
LRU Add Active Anon 2640587 2702818
LRU Add Inactive File 8833662 8068353
LRU Add Inactive Anon 207 200
Note that only pages on the local pagevec are considered on purpose. A
!PageLRU page could be in the process of being released, reclaimed,
migrated or on a remote pagevec that is currently being drained.
Marking it PageActive is vunerable to races where PageLRU and Active
bits are checked at the wrong time. Page reclaim will trigger
VM_BUG_ONs but depending on when the race hits, it could also free a
PageActive page to the page allocator and trigger a bad_page warning.
Similarly a potential race exists between a per-cpu drain on a pagevec
list and an activation on a remote CPU.
lru_add_drain_cpu
__pagevec_lru_add
lru = page_lru(page);
mark_page_accessed
if (PageLRU(page))
activate_page
else
SetPageActive
SetPageLRU(page);
add_page_to_lru_list(page, lruvec, lru);
In this case a PageActive page is added to the inactivate list and later
the inactive/active stats will get skewed. While the PageActive checks
in vmscan could be removed and potentially dealt with, a skew in the
statistics would be very difficult to detect. Hence this patch deals
just with the common case where a page being marked accessed has just
been added to the local pagevec.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Jan Kara <jack@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alexey Lyahkov <alexey.lyashkov@gmail.com>
Cc: Andrew Perepechko <anserper@ya.ru>
Cc: Robin Dong <sanbai@taobao.com>
Cc: Theodore Tso <tytso@mit.edu>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Bernd Schubert <bernd.schubert@fastmail.fm>
Cc: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mark_page_accessed() cannot activate an inactive page that is located on
an inactive LRU pagevec. Hints from filesystems may be ignored as a
result. In preparation for fixing that problem, this patch removes the
per-LRU pagevecs and leaves just one pagevec. The final LRU the page is
added to is deferred until the pagevec is drained.
This means that fewer pagevecs are available and potentially there is
greater contention on the LRU lock. However, this only applies in the
case where there is an almost perfect mix of file, anon, active and
inactive pages being added to the LRU. In practice I expect that we are
adding stream of pages of a particular time and that the changes in
contention will barely be measurable.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alexey Lyahkov <alexey.lyashkov@gmail.com>
Cc: Andrew Perepechko <anserper@ya.ru>
Cc: Robin Dong <sanbai@taobao.com>
Cc: Theodore Tso <tytso@mit.edu>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Bernd Schubert <bernd.schubert@fastmail.fm>
Cc: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andrew Perepechko reported a problem whereby pages are being prematurely
evicted as the mark_page_accessed() hint is ignored for pages that are
currently on a pagevec --
http://www.spinics.net/lists/linux-ext4/msg37340.html .
Alexey Lyahkov and Robin Dong have also reported problems recently that
could be due to hot pages reaching the end of the inactive list too
quickly and be reclaimed.
Rather than addressing this on a per-filesystem basis, this series aims
to fix the mark_page_accessed() interface by deferring what LRU a page
is added to pagevec drain time and allowing mark_page_accessed() to call
SetPageActive on a pagevec page.
Patch 1 adds two tracepoints for LRU page activation and insertion. Using
these processes it's possible to build a model of pages in the
LRU that can be processed offline.
Patch 2 defers making the decision on what LRU to add a page to until when
the pagevec is drained.
Patch 3 searches the local pagevec for pages to mark PageActive on
mark_page_accessed. The changelog explains why only the local
pagevec is examined.
Patches 4 and 5 tidy up the API.
postmark, a dd-based test and fs-mark both single and threaded mode were
run but none of them showed any performance degradation or gain as a
result of the patch.
Using patch 1, I built a *very* basic model of the LRU to examine
offline what the average age of different page types on the LRU were in
milliseconds. Of course, capturing the trace distorts the test as it's
written to local disk but it does not matter for the purposes of this
test. The average age of pages in milliseconds were
vanilla deferdrain
Average age mapped anon: 1454 1250
Average age mapped file: 127841 155552
Average age unmapped anon: 85 235
Average age unmapped file: 73633 38884
Average age unmapped buffers: 74054 116155
The LRU activity was mostly files which you'd expect for a dd-based
workload. Note that the average age of buffer pages is increased by the
series and it is expected this is due to the fact that the buffer pages
are now getting added to the active list when drained from the pagevecs.
Note that the average age of the unmapped file data is decreased as they
are still added to the inactive list and are reclaimed before the
buffers.
There is no guarantee this is a universal win for all workloads and it
would be nice if the filesystem people gave some thought as to whether
this decision is generally a win or a loss.
This patch:
Using these tracepoints it is possible to model LRU activity and the
average residency of pages of different types. This can be used to
debug problems related to premature reclaim of pages of particular
types.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alexey Lyahkov <alexey.lyashkov@gmail.com>
Cc: Andrew Perepechko <anserper@ya.ru>
Cc: Robin Dong <sanbai@taobao.com>
Cc: Theodore Tso <tytso@mit.edu>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Bernd Schubert <bernd.schubert@fastmail.fm>
Cc: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In page reclaim, huge page is split. split_huge_page() adds tail pages
to LRU list. Since we are reclaiming a huge page, it's better we
reclaim all subpages of the huge page instead of just the head page.
This patch adds split tail pages to shrink page list so the tail pages
can be reclaimed soon.
Before this patch, run a swap workload:
thp_fault_alloc 3492
thp_fault_fallback 608
thp_collapse_alloc 6
thp_collapse_alloc_failed 0
thp_split 916
With this patch:
thp_fault_alloc 4085
thp_fault_fallback 16
thp_collapse_alloc 90
thp_collapse_alloc_failed 0
thp_split 1272
fallback allocation is reduced a lot.
[akpm@linux-foundation.org: fix CONFIG_SWAP=n build]
Signed-off-by: Shaohua Li <shli@fusionio.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When I use several fast SSD to do swap, swapper_space.tree_lock is
heavily contended. This makes each swap partition have one
address_space to reduce the lock contention. There is an array of
address_space for swap. The swap entry type is the index to the array.
In my test with 3 SSD, this increases the swapout throughput 20%.
[akpm@linux-foundation.org: revert unneeded change to __add_to_swap_cache]
Signed-off-by: Shaohua Li <shli@fusionio.com>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
page_evictable(page, vma) is an irritant: almost all its callers pass
NULL for vma. Remove the vma arg and use mlocked_vma_newpage(vma, page)
explicitly in the couple of places it's needed. But in those places we
don't even need page_evictable() itself! They're dealing with a freshly
allocated anonymous page, which has no "mapping" and cannot be mlocked yet.
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When writing a new file with 2048 bytes buffer, such as write(fd, buffer,
2048), it will call generic_perform_write() twice for every page:
write_begin
mark_page_accessed(page)
write_end
write_begin
mark_page_accessed(page)
write_end
Pages 1-13 will be added to lru-pvecs in write_begin() and will *NOT* be
added to active_list even they have be accessed twice because they are not
PageLRU(page). But when page 14th comes, all pages in lru-pvecs will be
moved to inactive_list (by __lru_cache_add() ) in first write_begin(), now
page 14th *is* PageLRU(page). And after second write_end() only page 14th
will be in active_list.
In Hadoop environment, we do comes to this situation: after writing a
file, we find out that only 14th, 28th, 42th... page are in active_list
and others in inactive_list. Now kswapd works, shrinks the inactive_list,
the file only have 14th, 28th...pages in memory, the readahead request
size will be broken to only 52k (13*4k), system's performance falls
dramatically.
This problem can also replay by below steps (the machine has 8G memory):
1. dd if=/dev/zero of=/test/file.out bs=1024 count=1048576
2. cat another 7.5G file to /dev/null
3. vmtouch -m 1G -v /test/file.out, it will show:
/test/file.out
[oooooooooooooooooooOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO] 187847/262144
the 'o' means same pages are in memory but same are not.
The solution for this problem is simple: the 14th page should be added to
lru_add_pvecs before mark_page_accessed() just as other pages.
[akpm@linux-foundation.org: tweak comment]
[akpm@linux-foundation.org: grab better comment from the v3 patch]
Signed-off-by: Robin Dong <sanbai@taobao.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The patch "mm: add support for a filesystem to activate swap files and use
direct_IO for writing swap pages" added support for using direct_IO to
write swap pages but it is insufficient for highmem pages.
To support highmem pages, this patch kmaps() the page before calling the
direct_IO() handler. As direct_IO deals with virtual addresses an
additional helper is necessary for get_kernel_pages() to lookup the struct
page for a kmap virtual address.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Eric Paris <eparis@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Neil Brown <neilb@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Xiaotian Feng <dfeng@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch adds two new APIs get_kernel_pages() and get_kernel_page() that
may be used to pin a vector of kernel addresses for IO. The initial user
is expected to be NFS for allowing pages to be written to swap using
aops->direct_IO(). Strictly speaking, swap-over-NFS only needs to pin one
page for IO but it makes sense to express the API in terms of a vector and
add a helper for pinning single pages.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Eric Paris <eparis@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Neil Brown <neilb@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Xiaotian Feng <dfeng@redhat.com>
Cc: Mark Salter <msalter@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Take lruvec further: pass it instead of zone to add_page_to_lru_list() and
del_page_from_lru_list(); and pagevec_lru_move_fn() pass lruvec down to
its target functions.
This cleanup eliminates a swathe of cruft in memcontrol.c, including
mem_cgroup_lru_add_list(), mem_cgroup_lru_del_list() and
mem_cgroup_lru_move_lists() - which never actually touched the lists.
In their place, mem_cgroup_page_lruvec() to decide the lruvec, previously
a side-effect of add, and mem_cgroup_update_lru_size() to maintain the
lru_size stats.
Whilst these are simplifications in their own right, the goal is to bring
the evaluation of lruvec next to the spin_locking of the lrus, in
preparation for a future patch.
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With mem_cgroup_disabled() now explicit, it becomes clear that the
zone_reclaim_stat structure actually belongs in lruvec, per-zone when
memcg is disabled but per-memcg per-zone when it's enabled.
We can delete mem_cgroup_get_reclaim_stat(), and change
update_page_reclaim_stat() to update just the one set of stats, the one
which get_scan_count() will actually use.
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Transparent huge pages can change page->flags (PG_compound_lock) without
taking Slab lock. Since THP can not break slab pages we can safely access
compound page without taking compound lock.
Specifically this patch fixes a race between compound_unlock() and slab
functions which perform page-flags updates. This can occur when
get_page()/put_page() is called on a page from slab.
[akpm@linux-foundation.org: tweak comment text, fix comment layout, fix label indenting]
Reported-by: Amey Bhide <abhide@nicira.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Acked-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This cpu hotplug hook was accidentally removed in commit 00a62ce91e
("mm: fix Committed_AS underflow on large NR_CPUS environment")
The visible effect of this accident: some pages are borrowed in per-cpu
page-vectors. Truncate can deal with it, but these pages cannot be
reused while this cpu is offline. So this is like a temporary memory
leak.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Eric B Munson <ebmunson@us.ibm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When moving tasks from old memcg (with move_charge_at_immigrate on new
memcg), followed by removal of old memcg, hit General Protection Fault in
mem_cgroup_lru_del_list() (called from release_pages called from
free_pages_and_swap_cache from tlb_flush_mmu from tlb_finish_mmu from
exit_mmap from mmput from exit_mm from do_exit).
Somewhat reproducible, takes a few hours: the old struct mem_cgroup has
been freed and poisoned by SLAB_DEBUG, but mem_cgroup_lru_del_list() is
still trying to update its stats, and take page off lru before freeing.
A task, or a charge, or a page on lru: each secures a memcg against
removal. In this case, the last task has been moved out of the old memcg,
and it is exiting: anonymous pages are uncharged one by one from the
memcg, as they are zapped from its pagetables, so the charge gets down to
0; but the pages themselves are queued in an mmu_gather for freeing.
Most of those pages will be on lru (and force_empty is careful to
lru_add_drain_all, to add pages from pagevec to lru first), but not
necessarily all: perhaps some have been isolated for page reclaim, perhaps
some isolated for other reasons. So, force_empty may find no task, no
charge and no page on lru, and let the removal proceed.
There would still be no problem if these pages were immediately freed; but
typically (and the put_page_testzero protocol demands it) they have to be
added back to lru before they are found freeable, then removed from lru
and freed. We don't see the issue when adding, because the
mem_cgroup_iter() loops keep their own reference to the memcg being
scanned; but when it comes to mem_cgroup_lru_del_list().
I believe this was not an issue in v3.2: there, PageCgroupAcctLRU and
PageCgroupUsed flags were used (like a trick with mirrors) to deflect view
of pc->mem_cgroup to the stable root_mem_cgroup when neither set.
38c5d72f3e ("memcg: simplify LRU handling by new rule") mercifully
removed those convolutions, but left this General Protection Fault.
But it's surprisingly easy to restore the old behaviour: just check
PageCgroupUsed in mem_cgroup_lru_add_list() (which decides on which lruvec
to add), and reset pc to root_mem_cgroup if page is uncharged. A risky
change? just going back to how it worked before; testing, and an audit of
uses of pc->mem_cgroup, show no problem.
And there's a nice bonus: with mem_cgroup_lru_add_list() itself making
sure that an uncharged page goes to root lru, mem_cgroup_reset_owner() no
longer has any purpose, and we can safely revert 4e5f01c2b9 ("memcg:
clear pc->mem_cgroup if necessary").
Calling update_page_reclaim_stat() after add_page_to_lru_list() in swap.c
is not strictly necessary: the lru_lock there, with RCU before memcg
structures are freed, makes mem_cgroup_get_reclaim_stat_from_page safe
without that; but it seems cleaner to rely on one dependency less.
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix CONFIG_TRANSPARENT_HUGEPAGE=y CONFIG_SMP=n CONFIG_DEBUG_VM=y
CONFIG_DEBUG_SPINLOCK=n kernel: spin_is_locked() is then always false,
and so triggers some BUGs in Transparent HugePage codepaths.
asm-generic/bug.h mentions this problem, and provides a WARN_ON_SMP(x);
but being too lazy to add VM_BUG_ON_SMP, BUG_ON_SMP, WARN_ON_SMP_ONCE,
VM_WARN_ON_SMP_ONCE, just test NR_CPUS != 1 in the existing VM_BUG_ONs.
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
del_page_from_lru() repeats del_page_from_lru_list(), also working out
which LRU the page was on, clearing the relevant bits. Decouple those
functions: remove del_page_from_lru() and add page_off_lru().
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
checkpatch rightly protests
WARNING: EXPORT_SYMBOL(foo); should immediately follow its function/variable
so fix the five offenders in mm/swap.c.
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
What's so special about ____pagevec_lru_add() that it needs four leading
underscores? Nothing, it just helped to distinguish from
__pagevec_lru_add() in 2.6.28 development. Cut two leading underscores.
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Replace pagevecs in putback_lru_pages() and move_active_pages_to_lru()
by lists of pages_to_free: then apply Konstantin Khlebnikov's
free_hot_cold_page_list() to them instead of pagevec_release().
Which simplifies the flow (no need to drop and retake lock whenever
pagevec fills up) and reduces stale addresses in stack backtraces
(which often showed through the pagevecs); but more importantly,
removes another 120 bytes from the deepest stacks in page reclaim.
Although I've not recently seen an actual stack overflow here with
a vanilla kernel, move_active_pages_to_lru() has often featured in
deep backtraces.
However, free_hot_cold_page_list() does not handle compound pages
(nor need it: a Transparent HugePage would have been split by the
time it reaches the call in shrink_page_list()), but it is possible
for putback_lru_pages() or move_active_pages_to_lru() to be left
holding the last reference on a THP, so must exclude the unlikely
compound case before putting on pages_to_free.
Remove pagevec_strip(), its work now done in move_active_pages_to_lru().
The pagevec in scan_mapping_unevictable_pages() remains in mm/vmscan.c,
but that is never on the reclaim path, and cannot be replaced by a list.
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch started off as a cleanup: __split_huge_page_refcounts() has to
cope with two scenarios, when the hugepage being split is already on LRU,
and when it is not; but why does it have to split that accounting across
three different sites? Consolidate it in lru_add_page_tail(), handling
evictable and unevictable alike, and use standard add_page_to_lru_list()
when accounting is needed (when the head is not yet on LRU).
But a recent regression in -next, I guess the removal of PageCgroupAcctLRU
test from mem_cgroup_split_huge_fixup(), makes this now a necessary fix:
under load, the MEM_CGROUP_ZSTAT count was wrapping to a huge number,
messing up reclaim calculations and causing a freeze at rmdir of cgroup.
Add a VM_BUG_ON to mem_cgroup_lru_del_list() when we're about to wrap that
count - this has not been the only such incident. Document that
lru_add_page_tail() is for Transparent HugePages by #ifdef around it.
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Put the tail subpages of an isolated hugepage under splitting in the lru
reclaim head as they supposedly should be isolated too next.
Queues the subpages in physical order in the lru for non isolated
hugepages under splitting. That might provide some theoretical cache
benefit to the buddy allocator later.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now that all code that operated on global per-zone LRU lists is
converted to operate on per-memory cgroup LRU lists instead, there is no
reason to keep the double-LRU scheme around any longer.
The pc->lru member is removed and page->lru is linked directly to the
per-memory cgroup LRU lists, which removes two pointers from a
descriptor that exists for every page frame in the system.
Signed-off-by: Johannes Weiner <jweiner@redhat.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Ying Han <yinghan@google.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Having a unified structure with a LRU list set for both global zones and
per-memcg zones allows to keep that code simple which deals with LRU
lists and does not care about the container itself.
Once the per-memcg LRU lists directly link struct pages, the isolation
function and all other list manipulations are shared between the memcg
case and the global LRU case.
Signed-off-by: Johannes Weiner <jweiner@redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Ying Han <yinghan@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux: (230 commits)
Revert "tracing: Include module.h in define_trace.h"
irq: don't put module.h into irq.h for tracking irqgen modules.
bluetooth: macroize two small inlines to avoid module.h
ip_vs.h: fix implicit use of module_get/module_put from module.h
nf_conntrack.h: fix up fallout from implicit moduleparam.h presence
include: replace linux/module.h with "struct module" wherever possible
include: convert various register fcns to macros to avoid include chaining
crypto.h: remove unused crypto_tfm_alg_modname() inline
uwb.h: fix implicit use of asm/page.h for PAGE_SIZE
pm_runtime.h: explicitly requires notifier.h
linux/dmaengine.h: fix implicit use of bitmap.h and asm/page.h
miscdevice.h: fix up implicit use of lists and types
stop_machine.h: fix implicit use of smp.h for smp_processor_id
of: fix implicit use of errno.h in include/linux/of.h
of_platform.h: delete needless include <linux/module.h>
acpi: remove module.h include from platform/aclinux.h
miscdevice.h: delete unnecessary inclusion of module.h
device_cgroup.h: delete needless include <linux/module.h>
net: sch_generic remove redundant use of <linux/module.h>
net: inet_timewait_sock doesnt need <linux/module.h>
...
Fix up trivial conflicts (other header files, and removal of the ab3550 mfd driver) in
- drivers/media/dvb/frontends/dibx000_common.c
- drivers/media/video/{mt9m111.c,ov6650.c}
- drivers/mfd/ab3550-core.c
- include/linux/dmaengine.h
Michel while working on the working set estimation code, noticed that
calling get_page_unless_zero() on a random pfn_to_page(random_pfn)
wasn't safe, if the pfn ended up being a tail page of a transparent
hugepage under splitting by __split_huge_page_refcount().
He then found the problem could also theoretically materialize with
page_cache_get_speculative() during the speculative radix tree lookups
that uses get_page_unless_zero() in SMP if the radix tree page is freed
and reallocated and get_user_pages is called on it before
page_cache_get_speculative has a chance to call get_page_unless_zero().
So the best way to fix the problem is to keep page_tail->_count zero at
all times. This will guarantee that get_page_unless_zero() can never
succeed on any tail page. page_tail->_mapcount is guaranteed zero and
is unused for all tail pages of a compound page, so we can simply
account the tail page references there and transfer them to
tail_page->_count in __split_huge_page_refcount() (in addition to the
head_page->_mapcount).
While debugging this s/_count/_mapcount/ change I also noticed get_page is
called by direct-io.c on pages returned by get_user_pages. That wasn't
entirely safe because the two atomic_inc in get_page weren't atomic. As
opposed to other get_user_page users like secondary-MMU page fault to
establish the shadow pagetables would never call any superflous get_page
after get_user_page returns. It's safer to make get_page universally safe
for tail pages and to use get_page_foll() within follow_page (inside
get_user_pages()). get_page_foll() is safe to do the refcounting for tail
pages without taking any locks because it is run within PT lock protected
critical sections (PT lock for pte and page_table_lock for
pmd_trans_huge).
The standard get_page() as invoked by direct-io instead will now take
the compound_lock but still only for tail pages. The direct-io paths
are usually I/O bound and the compound_lock is per THP so very
finegrined, so there's no risk of scalability issues with it. A simple
direct-io benchmarks with all lockdep prove locking and spinlock
debugging infrastructure enabled shows identical performance and no
overhead. So it's worth it. Ideally direct-io should stop calling
get_page() on pages returned by get_user_pages(). The spinlock in
get_page() is already optimized away for no-THP builds but doing
get_page() on tail pages returned by GUP is generally a rare operation
and usually only run in I/O paths.
This new refcounting on page_tail->_mapcount in addition to avoiding new
RCU critical sections will also allow the working set estimation code to
work without any further complexity associated to the tail page
refcounting with THP.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: Michel Lespinasse <walken@google.com>
Reviewed-by: Michel Lespinasse <walken@google.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: <stable@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The files changed within are only using the EXPORT_SYMBOL
macro variants. They are not using core modular infrastructure
and hence don't need module.h but only the export.h header.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
The zone->lru_lock is heavily contented in workload where activate_page()
is frequently used. We could do batch activate_page() to reduce the lock
contention. The batched pages will be added into zone list when the pool
is full or page reclaim is trying to drain them.
For example, in a 4 socket 64 CPU system, create a sparse file and 64
processes, processes shared map to the file. Each process read access the
whole file and then exit. The process exit will do unmap_vmas() and cause
a lot of activate_page() call. In such workload, we saw about 58% total
time reduction with below patch. Other workloads with a lot of
activate_page also benefits a lot too.
Andrew Morton suggested activate_page() and putback_lru_pages() should
follow the same path to active pages, but this is hard to implement (see
commit 7a608572a2 ("Revert "mm: batch activate_page() to reduce lock
contention")). On the other hand, do we really need putback_lru_pages()
to follow the same path? I tested several FIO/FFSB benchmark (about 20
scripts for each benchmark) in 3 machines here from 2 sockets to 4
sockets. My test doesn't show anything significant with/without below
patch (there is slight difference but mostly some noise which we found
even without below patch before). Below patch basically returns to the
same as my first post.
I tested some microbenchmarks:
case-anon-cow-rand-mt 0.58%
case-anon-cow-rand -3.30%
case-anon-cow-seq-mt -0.51%
case-anon-cow-seq -5.68%
case-anon-r-rand-mt 0.23%
case-anon-r-rand 0.81%
case-anon-r-seq-mt -0.71%
case-anon-r-seq -1.99%
case-anon-rx-rand-mt 2.11%
case-anon-rx-seq-mt 3.46%
case-anon-w-rand-mt -0.03%
case-anon-w-rand -0.50%
case-anon-w-seq-mt -1.08%
case-anon-w-seq -0.12%
case-anon-wx-rand-mt -5.02%
case-anon-wx-seq-mt -1.43%
case-fork 1.65%
case-fork-sleep -0.07%
case-fork-withmem 1.39%
case-hugetlb -0.59%
case-lru-file-mmap-read-mt -0.54%
case-lru-file-mmap-read 0.61%
case-lru-file-mmap-read-rand -2.24%
case-lru-file-readonce -0.64%
case-lru-file-readtwice -11.69%
case-lru-memcg -1.35%
case-mmap-pread-rand-mt 1.88%
case-mmap-pread-rand -15.26%
case-mmap-pread-seq-mt 0.89%
case-mmap-pread-seq -69.72%
case-mmap-xread-rand-mt 0.71%
case-mmap-xread-seq-mt 0.38%
The most significent are:
case-lru-file-readtwice -11.69%
case-mmap-pread-rand -15.26%
case-mmap-pread-seq -69.72%
which use activate_page a lot. others are basically variations because
each run has slightly difference.
In UP case, 'size mm/swap.o'
before the two patches:
text data bss dec hex filename
6466 896 4 7366 1cc6 mm/swap.o
after the two patches:
text data bss dec hex filename
6343 896 4 7243 1c4b mm/swap.o
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It's pointless that deactive_page's operates on unevictable pages. This
patch removes unnecessary overhead which might be a bit problem in case
that there are many unevictable page in system(ex, mprotect workload)
[akpm@linux-foundation.org: tidy up comment]
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: Rik van Riel<riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The lru_deactivate_fn should not move page which in on unevictable lru
into inactive list. Otherwise, we can meet BUG when we use
isolate_lru_pages as __isolate_lru_page could return -EINVAL.
Reported-by: Ying Han <yinghan@google.com>
Tested-by: Ying Han <yinghan@google.com>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Rik van Riel<riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
invalidate_mapping_pages is very big hint to reclaimer. It means user
doesn't want to use the page any more. So in order to prevent working set
page eviction, this patch move the page into tail of inactive list by
PG_reclaim.
Please, remember that pages in inactive list are working set as well as
active list. If we don't move pages into inactive list's tail, pages near
by tail of inactive list can be evicted although we have a big clue about
useless pages. It's totally bad.
Now PG_readahead/PG_reclaim is shared. fe3cba17 added ClearPageReclaim
into clear_page_dirty_for_io for preventing fast reclaiming readahead
marker page.
In this series, PG_reclaim is used by invalidated page, too. If VM find
the page is invalidated and it's dirty, it sets PG_reclaim to reclaim
asap. Then, when the dirty page will be writeback,
clear_page_dirty_for_io will clear PG_reclaim unconditionally. It
disturbs this serie's goal.
I think it's okay to clear PG_readahead when the page is dirty, not
writeback time. So this patch moves ClearPageReadahead. In v4,
ClearPageReadahead in set_page_dirty has a problem which is reported by
Steven Barrett. It's due to compound page. Some driver(ex, audio) calls
set_page_dirty with compound page which isn't on LRU. but my patch does
ClearPageRelcaim on compound page. In non-CONFIG_PAGEFLAGS_EXTENDED, it
breaks PageTail flag.
I think it doesn't affect THP and pass my test with THP enabling but Cced
Andrea for double check.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Reported-by: Steven Barrett <damentz@liquorix.net>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The rotate_reclaimable_page function moves just written out pages, which
the VM wanted to reclaim, to the end of the inactive list. That way the
VM will find those pages first next time it needs to free memory.
This patch applies the rule in memcg. It can help to prevent unnecessary
working page eviction of memcg.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Recently, there are reported problem about thrashing.
(http://marc.info/?l=rsync&m=128885034930933&w=2) It happens by backup
workloads(ex, nightly rsync). That's because the workload makes just
use-once pages and touches pages twice. It promotes the page into active
list so that it results in working set page eviction.
Some app developer want to support POSIX_FADV_NOREUSE. But other OSes
don't support it, either.
(http://marc.info/?l=linux-mm&m=128928979512086&w=2)
By other approach, app developers use POSIX_FADV_DONTNEED. But it has a
problem. If kernel meets page is writing during invalidate_mapping_pages,
it can't work. It makes for application programmer to use it since they
always have to sync data before calling fadivse(..POSIX_FADV_DONTNEED) to
make sure the pages could be discardable. At last, they can't use
deferred write of kernel so that they could see performance loss.
(http://insights.oetiker.ch/linux/fadvise.html)
In fact, invalidation is very big hint to reclaimer. It means we don't
use the page any more. So let's move the writing page into inactive
list's head if we can't truncate it right now.
Why I move page to head of lru on this patch, Dirty/Writeback page would
be flushed sooner or later. It can prevent writeout of pageout which is
less effective than flusher's writeout.
Originally, I reused lru_demote of Peter with some change so added his
Signed-off-by.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Reported-by: Ben Gamari <bgamari.foss@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This reverts commit d8505dee1a.
Chris Mason ended up chasing down some page allocation errors and pages
stuck waiting on the IO scheduler, and was able to narrow it down to two
commits: commit 744ed14427 ("mm: batch activate_page() to reduce lock
contention") and d8505dee1a ("mm: simplify code of swap.c").
This reverts the second one.
Reported-and-debugged-by: Chris Mason <chris.mason@oracle.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <jaxboe@fusionio.com>
Cc: linux-mm <linux-mm@kvack.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This reverts commit 744ed14427.
Chris Mason ended up chasing down some page allocation errors and pages
stuck waiting on the IO scheduler, and was able to narrow it down to two
commits: commit 744ed14427 ("mm: batch activate_page() to reduce lock
contention") and d8505dee1a ("mm: simplify code of swap.c").
This reverts the first of them.
Reported-and-debugged-by: Chris Mason <chris.mason@oracle.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <jaxboe@fusionio.com>
Cc: linux-mm <linux-mm@kvack.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The zone->lru_lock is heavily contented in workload where activate_page()
is frequently used. We could do batch activate_page() to reduce the lock
contention. The batched pages will be added into zone list when the pool
is full or page reclaim is trying to drain them.
For example, in a 4 socket 64 CPU system, create a sparse file and 64
processes, processes shared map to the file. Each process read access the
whole file and then exit. The process exit will do unmap_vmas() and cause
a lot of activate_page() call. In such workload, we saw about 58% total
time reduction with below patch. Other workloads with a lot of
activate_page also benefits a lot too.
I tested some microbenchmarks:
case-anon-cow-rand-mt 0.58%
case-anon-cow-rand -3.30%
case-anon-cow-seq-mt -0.51%
case-anon-cow-seq -5.68%
case-anon-r-rand-mt 0.23%
case-anon-r-rand 0.81%
case-anon-r-seq-mt -0.71%
case-anon-r-seq -1.99%
case-anon-rx-rand-mt 2.11%
case-anon-rx-seq-mt 3.46%
case-anon-w-rand-mt -0.03%
case-anon-w-rand -0.50%
case-anon-w-seq-mt -1.08%
case-anon-w-seq -0.12%
case-anon-wx-rand-mt -5.02%
case-anon-wx-seq-mt -1.43%
case-fork 1.65%
case-fork-sleep -0.07%
case-fork-withmem 1.39%
case-hugetlb -0.59%
case-lru-file-mmap-read-mt -0.54%
case-lru-file-mmap-read 0.61%
case-lru-file-mmap-read-rand -2.24%
case-lru-file-readonce -0.64%
case-lru-file-readtwice -11.69%
case-lru-memcg -1.35%
case-mmap-pread-rand-mt 1.88%
case-mmap-pread-rand -15.26%
case-mmap-pread-seq-mt 0.89%
case-mmap-pread-seq -69.72%
case-mmap-xread-rand-mt 0.71%
case-mmap-xread-seq-mt 0.38%
The most significent are:
case-lru-file-readtwice -11.69%
case-mmap-pread-rand -15.26%
case-mmap-pread-seq -69.72%
which use activate_page a lot. others are basically variations because
each run has slightly difference.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Clean up code and remove duplicate code. Next patch will use
pagevec_lru_move_fn introduced here too.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Lately I've been working to make KVM use hugepages transparently without
the usual restrictions of hugetlbfs. Some of the restrictions I'd like to
see removed:
1) hugepages have to be swappable or the guest physical memory remains
locked in RAM and can't be paged out to swap
2) if a hugepage allocation fails, regular pages should be allocated
instead and mixed in the same vma without any failure and without
userland noticing
3) if some task quits and more hugepages become available in the
buddy, guest physical memory backed by regular pages should be
relocated on hugepages automatically in regions under
madvise(MADV_HUGEPAGE) (ideally event driven by waking up the
kernel deamon if the order=HPAGE_PMD_SHIFT-PAGE_SHIFT list becomes
not null)
4) avoidance of reservation and maximization of use of hugepages whenever
possible. Reservation (needed to avoid runtime fatal faliures) may be ok for
1 machine with 1 database with 1 database cache with 1 database cache size
known at boot time. It's definitely not feasible with a virtualization
hypervisor usage like RHEV-H that runs an unknown number of virtual machines
with an unknown size of each virtual machine with an unknown amount of
pagecache that could be potentially useful in the host for guest not using
O_DIRECT (aka cache=off).
hugepages in the virtualization hypervisor (and also in the guest!) are
much more important than in a regular host not using virtualization,
becasue with NPT/EPT they decrease the tlb-miss cacheline accesses from 24
to 19 in case only the hypervisor uses transparent hugepages, and they
decrease the tlb-miss cacheline accesses from 19 to 15 in case both the
linux hypervisor and the linux guest both uses this patch (though the
guest will limit the addition speedup to anonymous regions only for
now...). Even more important is that the tlb miss handler is much slower
on a NPT/EPT guest than for a regular shadow paging or no-virtualization
scenario. So maximizing the amount of virtual memory cached by the TLB
pays off significantly more with NPT/EPT than without (even if there would
be no significant speedup in the tlb-miss runtime).
The first (and more tedious) part of this work requires allowing the VM to
handle anonymous hugepages mixed with regular pages transparently on
regular anonymous vmas. This is what this patch tries to achieve in the
least intrusive possible way. We want hugepages and hugetlb to be used in
a way so that all applications can benefit without changes (as usual we
leverage the KVM virtualization design: by improving the Linux VM at
large, KVM gets the performance boost too).
The most important design choice is: always fallback to 4k allocation if
the hugepage allocation fails! This is the _very_ opposite of some large
pagecache patches that failed with -EIO back then if a 64k (or similar)
allocation failed...
Second important decision (to reduce the impact of the feature on the
existing pagetable handling code) is that at any time we can split an
hugepage into 512 regular pages and it has to be done with an operation
that can't fail. This way the reliability of the swapping isn't decreased
(no need to allocate memory when we are short on memory to swap) and it's
trivial to plug a split_huge_page* one-liner where needed without
polluting the VM. Over time we can teach mprotect, mremap and friends to
handle pmd_trans_huge natively without calling split_huge_page*. The fact
it can't fail isn't just for swap: if split_huge_page would return -ENOMEM
(instead of the current void) we'd need to rollback the mprotect from the
middle of it (ideally including undoing the split_vma) which would be a
big change and in the very wrong direction (it'd likely be simpler not to
call split_huge_page at all and to teach mprotect and friends to handle
hugepages instead of rolling them back from the middle). In short the
very value of split_huge_page is that it can't fail.
The collapsing and madvise(MADV_HUGEPAGE) part will remain separated and
incremental and it'll just be an "harmless" addition later if this initial
part is agreed upon. It also should be noted that locking-wise replacing
regular pages with hugepages is going to be very easy if compared to what
I'm doing below in split_huge_page, as it will only happen when
page_count(page) matches page_mapcount(page) if we can take the PG_lock
and mmap_sem in write mode. collapse_huge_page will be a "best effort"
that (unlike split_huge_page) can fail at the minimal sign of trouble and
we can try again later. collapse_huge_page will be similar to how KSM
works and the madvise(MADV_HUGEPAGE) will work similar to
madvise(MADV_MERGEABLE).
The default I like is that transparent hugepages are used at page fault
time. This can be changed with
/sys/kernel/mm/transparent_hugepage/enabled. The control knob can be set
to three values "always", "madvise", "never" which mean respectively that
hugepages are always used, or only inside madvise(MADV_HUGEPAGE) regions,
or never used. /sys/kernel/mm/transparent_hugepage/defrag instead
controls if the hugepage allocation should defrag memory aggressively
"always", only inside "madvise" regions, or "never".
The pmd_trans_splitting/pmd_trans_huge locking is very solid. The
put_page (from get_user_page users that can't use mmu notifier like
O_DIRECT) that runs against a __split_huge_page_refcount instead was a
pain to serialize in a way that would result always in a coherent page
count for both tail and head. I think my locking solution with a
compound_lock taken only after the page_first is valid and is still a
PageHead should be safe but it surely needs review from SMP race point of
view. In short there is no current existing way to serialize the O_DIRECT
final put_page against split_huge_page_refcount so I had to invent a new
one (O_DIRECT loses knowledge on the mapping status by the time gup_fast
returns so...). And I didn't want to impact all gup/gup_fast users for
now, maybe if we change the gup interface substantially we can avoid this
locking, I admit I didn't think too much about it because changing the gup
unpinning interface would be invasive.
If we ignored O_DIRECT we could stick to the existing compound refcounting
code, by simply adding a get_user_pages_fast_flags(foll_flags) where KVM
(and any other mmu notifier user) would call it without FOLL_GET (and if
FOLL_GET isn't set we'd just BUG_ON if nobody registered itself in the
current task mmu notifier list yet). But O_DIRECT is fundamental for
decent performance of virtualized I/O on fast storage so we can't avoid it
to solve the race of put_page against split_huge_page_refcount to achieve
a complete hugepage feature for KVM.
Swap and oom works fine (well just like with regular pages ;). MMU
notifier is handled transparently too, with the exception of the young bit
on the pmd, that didn't have a range check but I think KVM will be fine
because the whole point of hugepages is that EPT/NPT will also use a huge
pmd when they notice gup returns pages with PageCompound set, so they
won't care of a range and there's just the pmd young bit to check in that
case.
NOTE: in some cases if the L2 cache is small, this may slowdown and waste
memory during COWs because 4M of memory are accessed in a single fault
instead of 8k (the payoff is that after COW the program can run faster).
So we might want to switch the copy_huge_page (and clear_huge_page too) to
not temporal stores. I also extensively researched ways to avoid this
cache trashing with a full prefault logic that would cow in 8k/16k/32k/64k
up to 1M (I can send those patches that fully implemented prefault) but I
concluded they're not worth it and they add an huge additional complexity
and they remove all tlb benefits until the full hugepage has been faulted
in, to save a little bit of memory and some cache during app startup, but
they still don't improve substantially the cache-trashing during startup
if the prefault happens in >4k chunks. One reason is that those 4k pte
entries copied are still mapped on a perfectly cache-colored hugepage, so
the trashing is the worst one can generate in those copies (cow of 4k page
copies aren't so well colored so they trashes less, but again this results
in software running faster after the page fault). Those prefault patches
allowed things like a pte where post-cow pages were local 4k regular anon
pages and the not-yet-cowed pte entries were pointing in the middle of
some hugepage mapped read-only. If it doesn't payoff substantially with
todays hardware it will payoff even less in the future with larger l2
caches, and the prefault logic would blot the VM a lot. If one is
emebdded transparent_hugepage can be disabled during boot with sysfs or
with the boot commandline parameter transparent_hugepage=0 (or
transparent_hugepage=2 to restrict hugepages inside madvise regions) that
will ensure not a single hugepage is allocated at boot time. It is simple
enough to just disable transparent hugepage globally and let transparent
hugepages be allocated selectively by applications in the MADV_HUGEPAGE
region (both at page fault time, and if enabled with the
collapse_huge_page too through the kernel daemon).
This patch supports only hugepages mapped in the pmd, archs that have
smaller hugepages will not fit in this patch alone. Also some archs like
power have certain tlb limits that prevents mixing different page size in
the same regions so they will not fit in this framework that requires
"graceful fallback" to basic PAGE_SIZE in case of physical memory
fragmentation. hugetlbfs remains a perfect fit for those because its
software limits happen to match the hardware limits. hugetlbfs also
remains a perfect fit for hugepage sizes like 1GByte that cannot be hoped
to be found not fragmented after a certain system uptime and that would be
very expensive to defragment with relocation, so requiring reservation.
hugetlbfs is the "reservation way", the point of transparent hugepages is
not to have any reservation at all and maximizing the use of cache and
hugepages at all times automatically.
Some performance result:
vmx andrea # LD_PRELOAD=/usr/lib64/libhugetlbfs.so HUGETLB_MORECORE=yes HUGETLB_PATH=/mnt/huge/ ./largep
ages3
memset page fault 1566023
memset tlb miss 453854
memset second tlb miss 453321
random access tlb miss 41635
random access second tlb miss 41658
vmx andrea # LD_PRELOAD=/usr/lib64/libhugetlbfs.so HUGETLB_MORECORE=yes HUGETLB_PATH=/mnt/huge/ ./largepages3
memset page fault 1566471
memset tlb miss 453375
memset second tlb miss 453320
random access tlb miss 41636
random access second tlb miss 41637
vmx andrea # ./largepages3
memset page fault 1566642
memset tlb miss 453417
memset second tlb miss 453313
random access tlb miss 41630
random access second tlb miss 41647
vmx andrea # ./largepages3
memset page fault 1566872
memset tlb miss 453418
memset second tlb miss 453315
random access tlb miss 41618
random access second tlb miss 41659
vmx andrea # echo 0 > /proc/sys/vm/transparent_hugepage
vmx andrea # ./largepages3
memset page fault 2182476
memset tlb miss 460305
memset second tlb miss 460179
random access tlb miss 44483
random access second tlb miss 44186
vmx andrea # ./largepages3
memset page fault 2182791
memset tlb miss 460742
memset second tlb miss 459962
random access tlb miss 43981
random access second tlb miss 43988
============
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#define SIZE (3UL*1024*1024*1024)
int main()
{
char *p = malloc(SIZE), *p2;
struct timeval before, after;
gettimeofday(&before, NULL);
memset(p, 0, SIZE);
gettimeofday(&after, NULL);
printf("memset page fault %Lu\n",
(after.tv_sec-before.tv_sec)*1000000UL +
after.tv_usec-before.tv_usec);
gettimeofday(&before, NULL);
memset(p, 0, SIZE);
gettimeofday(&after, NULL);
printf("memset tlb miss %Lu\n",
(after.tv_sec-before.tv_sec)*1000000UL +
after.tv_usec-before.tv_usec);
gettimeofday(&before, NULL);
memset(p, 0, SIZE);
gettimeofday(&after, NULL);
printf("memset second tlb miss %Lu\n",
(after.tv_sec-before.tv_sec)*1000000UL +
after.tv_usec-before.tv_usec);
gettimeofday(&before, NULL);
for (p2 = p; p2 < p+SIZE; p2 += 4096)
*p2 = 0;
gettimeofday(&after, NULL);
printf("random access tlb miss %Lu\n",
(after.tv_sec-before.tv_sec)*1000000UL +
after.tv_usec-before.tv_usec);
gettimeofday(&before, NULL);
for (p2 = p; p2 < p+SIZE; p2 += 4096)
*p2 = 0;
gettimeofday(&after, NULL);
printf("random access second tlb miss %Lu\n",
(after.tv_sec-before.tv_sec)*1000000UL +
after.tv_usec-before.tv_usec);
return 0;
}
============
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
After releasing the compound_lock split_huge_page can still run and release the
page before put_page_testzero runs.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Alter compound get_page/put_page to keep references on subpages too, in
order to allow __split_huge_page_refcount to split an hugepage even while
subpages have been pinned by one of the get_user_pages() variants.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Replace iterated page_cache_release() with release_pages(), which is
faster and shorter.
Needs release_pages() to be exported to modules.
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Johannes Weiner