2008-10-19 11:28:16 +08:00
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#ifndef __LINUX_PAGE_CGROUP_H
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#define __LINUX_PAGE_CGROUP_H
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2011-03-24 07:42:30 +08:00
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enum {
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/* flags for mem_cgroup */
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mm: memcontrol: rewrite uncharge API
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>
2014-08-09 05:19:22 +08:00
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PCG_USED = 0x01, /* This page is charged to a memcg */
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PCG_MEM = 0x02, /* This page holds a memory charge */
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PCG_MEMSW = 0x04, /* This page holds a memory+swap charge */
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2011-03-24 07:42:30 +08:00
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};
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2014-08-09 05:19:26 +08:00
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struct pglist_data;
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2012-08-01 07:43:02 +08:00
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#ifdef CONFIG_MEMCG
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2014-08-09 05:19:26 +08:00
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struct mem_cgroup;
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2011-03-24 07:42:30 +08:00
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2008-10-19 11:28:16 +08:00
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/*
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* Page Cgroup can be considered as an extended mem_map.
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* A page_cgroup page is associated with every page descriptor. The
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* page_cgroup helps us identify information about the cgroup
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* All page cgroups are allocated at boot or memory hotplug event,
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* then the page cgroup for pfn always exists.
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*/
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struct page_cgroup {
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unsigned long flags;
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struct mem_cgroup *mem_cgroup;
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};
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2014-08-09 05:19:26 +08:00
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extern void pgdat_page_cgroup_init(struct pglist_data *pgdat);
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2009-06-12 15:33:53 +08:00
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#ifdef CONFIG_SPARSEMEM
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2014-08-09 05:19:26 +08:00
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static inline void page_cgroup_init_flatmem(void)
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2009-06-12 15:33:53 +08:00
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{
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}
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2014-08-09 05:19:26 +08:00
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extern void page_cgroup_init(void);
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2009-06-12 15:33:53 +08:00
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#else
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2014-08-09 05:19:26 +08:00
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extern void page_cgroup_init_flatmem(void);
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static inline void page_cgroup_init(void)
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2009-06-12 15:33:53 +08:00
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{
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}
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#endif
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2008-10-19 11:28:16 +08:00
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struct page_cgroup *lookup_page_cgroup(struct page *page);
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mm: memcontrol: rewrite uncharge API
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>
2014-08-09 05:19:22 +08:00
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static inline int PageCgroupUsed(struct page_cgroup *pc)
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2008-10-19 11:28:16 +08:00
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{
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mm: memcontrol: rewrite uncharge API
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>
2014-08-09 05:19:22 +08:00
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return !!(pc->flags & PCG_USED);
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2008-10-19 11:28:16 +08:00
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}
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2014-08-09 05:19:26 +08:00
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#else /* !CONFIG_MEMCG */
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2008-10-19 11:28:16 +08:00
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struct page_cgroup;
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2014-08-09 05:19:26 +08:00
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static inline void pgdat_page_cgroup_init(struct pglist_data *pgdat)
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2008-10-19 11:28:16 +08:00
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{
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}
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static inline struct page_cgroup *lookup_page_cgroup(struct page *page)
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{
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return NULL;
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}
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2008-10-23 05:15:05 +08:00
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static inline void page_cgroup_init(void)
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{
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}
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2014-08-09 05:19:26 +08:00
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static inline void page_cgroup_init_flatmem(void)
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2009-06-12 15:33:53 +08:00
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{
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}
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2012-08-01 07:43:02 +08:00
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#endif /* CONFIG_MEMCG */
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2009-01-08 10:07:58 +08:00
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#include <linux/swap.h>
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2009-09-20 18:50:44 +08:00
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2012-08-01 07:43:02 +08:00
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#ifdef CONFIG_MEMCG_SWAP
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2010-03-11 07:22:17 +08:00
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extern unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
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unsigned short old, unsigned short new);
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2009-04-03 07:57:45 +08:00
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extern unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id);
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2012-01-13 09:18:48 +08:00
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extern unsigned short lookup_swap_cgroup_id(swp_entry_t ent);
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2009-01-08 10:07:58 +08:00
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extern int swap_cgroup_swapon(int type, unsigned long max_pages);
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extern void swap_cgroup_swapoff(int type);
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#else
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static inline
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2009-04-03 07:57:45 +08:00
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unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id)
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2009-01-08 10:07:58 +08:00
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{
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2009-04-03 07:57:45 +08:00
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return 0;
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2009-01-08 10:07:58 +08:00
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}
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static inline
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2012-01-13 09:18:48 +08:00
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unsigned short lookup_swap_cgroup_id(swp_entry_t ent)
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2009-01-08 10:07:58 +08:00
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{
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2009-04-03 07:57:45 +08:00
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return 0;
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2009-01-08 10:07:58 +08:00
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}
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static inline int
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swap_cgroup_swapon(int type, unsigned long max_pages)
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{
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return 0;
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}
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static inline void swap_cgroup_swapoff(int type)
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{
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return;
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}
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2012-08-01 07:43:02 +08:00
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#endif /* CONFIG_MEMCG_SWAP */
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2011-03-24 07:42:30 +08:00
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#endif /* __LINUX_PAGE_CGROUP_H */
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