linux/arch/mn10300/mm
Michal Hocko 32d6bd9059 tree wide: get rid of __GFP_REPEAT for order-0 allocations part I
This is the third version of the patchset previously sent [1].  I have
basically only rebased it on top of 4.7-rc1 tree and dropped "dm: get
rid of superfluous gfp flags" which went through dm tree.  I am sending
it now because it is tree wide and chances for conflicts are reduced
considerably when we want to target rc2.  I plan to send the next step
and rename the flag and move to a better semantic later during this
release cycle so we will have a new semantic ready for 4.8 merge window
hopefully.

Motivation:

While working on something unrelated I've checked the current usage of
__GFP_REPEAT in the tree.  It seems that a majority of the usage is and
always has been bogus because __GFP_REPEAT has always been about costly
high order allocations while we are using it for order-0 or very small
orders very often.  It seems that a big pile of them is just a
copy&paste when a code has been adopted from one arch to another.

I think it makes some sense to get rid of them because they are just
making the semantic more unclear.  Please note that GFP_REPEAT is
documented as

* __GFP_REPEAT: Try hard to allocate the memory, but the allocation attempt

* _might_ fail.  This depends upon the particular VM implementation.
  while !costly requests have basically nofail semantic.  So one could
  reasonably expect that order-0 request with __GFP_REPEAT will not loop
  for ever.  This is not implemented right now though.

I would like to move on with __GFP_REPEAT and define a better semantic
for it.

  $ git grep __GFP_REPEAT origin/master | wc -l
  111
  $ git grep __GFP_REPEAT | wc -l
  36

So we are down to the third after this patch series.  The remaining
places really seem to be relying on __GFP_REPEAT due to large allocation
requests.  This still needs some double checking which I will do later
after all the simple ones are sorted out.

I am touching a lot of arch specific code here and I hope I got it right
but as a matter of fact I even didn't compile test for some archs as I
do not have cross compiler for them.  Patches should be quite trivial to
review for stupid compile mistakes though.  The tricky parts are usually
hidden by macro definitions and thats where I would appreciate help from
arch maintainers.

[1] http://lkml.kernel.org/r/1461849846-27209-1-git-send-email-mhocko@kernel.org

This patch (of 19):

__GFP_REPEAT has a rather weak semantic but since it has been introduced
around 2.6.12 it has been ignored for low order allocations.  Yet we
have the full kernel tree with its usage for apparently order-0
allocations.  This is really confusing because __GFP_REPEAT is
explicitly documented to allow allocation failures which is a weaker
semantic than the current order-0 has (basically nofail).

Let's simply drop __GFP_REPEAT from those places.  This would allow to
identify place which really need allocator to retry harder and formulate
a more specific semantic for what the flag is supposed to do actually.

Link: http://lkml.kernel.org/r/1464599699-30131-2-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen Liqin <liqin.linux@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com> [for tile]
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: John Crispin <blogic@openwrt.org>
Cc: Lennox Wu <lennox.wu@gmail.com>
Cc: Ley Foon Tan <lftan@altera.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-06-24 17:23:52 -07:00
..
Kconfig.cache MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
Makefile MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-dbg-flush-by-reg.S MN10300: Fix one of the kernel debugger cacheflush variants 2011-06-07 19:03:52 -07:00
cache-dbg-flush-by-tag.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-dbg-inv-by-reg.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-dbg-inv-by-tag.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-dbg-inv.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-disabled.c MN10300: Handle missing sys_cacheflush() when caching disabled 2010-09-28 18:01:14 -07:00
cache-flush-by-reg.S MN10300: AM34: Add cacheflushing by using the AM34 purge registers 2010-10-27 17:28:45 +01:00
cache-flush-by-tag.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-flush-icache.c MN10300: Cache: Implement SMP global cache flushing 2010-10-27 17:28:47 +01:00
cache-inv-by-reg.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-inv-by-tag.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-inv-icache.c MN10300: The SMP_ICACHE_INV_FLUSH_RANGE IPI command does not exist 2011-03-14 14:45:29 +00:00
cache-smp-flush.c MN10300: Cache: Implement SMP global cache flushing 2010-10-27 17:28:47 +01:00
cache-smp-inv.c MN10300: Cache: Implement SMP global cache flushing 2010-10-27 17:28:47 +01:00
cache-smp.c mn10300: convert old cpumask API into new one 2011-05-25 08:39:39 -07:00
cache-smp.h MN10300: Cache: Implement SMP global cache flushing 2010-10-27 17:28:47 +01:00
cache.c MN10300: Cache: Implement SMP global cache flushing 2010-10-27 17:28:47 +01:00
cache.inc MN10300: The icache invalidate functions should disable the icache first 2011-03-18 16:54:29 +00:00
dma-alloc.c mn10300: convert to dma_map_ops 2016-01-20 17:09:18 -08:00
extable.c mn10300: add the MN10300/AM33 architecture to the kernel 2008-02-08 09:22:30 -08:00
fault.c mm/fault, arch: Use pagefault_disable() to check for disabled pagefaults in the handler 2015-05-19 08:39:15 +02:00
init.c mm/mn10300: prepare for removing num_physpages and simplify mem_init() 2013-07-03 16:07:37 -07:00
misalignment.c Disintegrate asm/system.h for MN10300 2012-03-28 18:30:02 +01:00
mmu-context.c MN10300: Make the use of PIDR to mark TLB entries controllable 2010-10-27 17:28:49 +01:00
pgtable.c tree wide: get rid of __GFP_REPEAT for order-0 allocations part I 2016-06-24 17:23:52 -07:00
tlb-mn10300.S MN10300: Use the [ID]PTEL2 registers rather than [ID]PTEL for TLB control 2010-10-27 17:28:50 +01:00
tlb-smp.c atomic: Replace atomic_{set,clear}_mask() usage 2015-07-27 14:06:24 +02:00