linux-stable.git/mm/page_alloc.c, branch linux-2.6.32.y

mm/page_alloc.c: prevent unending loop in __alloc_pages_slowpath()

2011-06-23T22:24:02+00:00

commit cfa54a0fcfc1017c6f122b6f21aaba36daa07f71 upstream.

I believe I found a problem in __alloc_pages_slowpath, which allows a
process to get stuck endlessly looping, even when lots of memory is
available.

Running an I/O and memory intensive stress-test I see a 0-order page
allocation with __GFP_IO and __GFP_WAIT, running on a system with very
little free memory.  Right about the same time that the stress-test gets
killed by the OOM-killer, the utility trying to allocate memory gets stuck
in __alloc_pages_slowpath even though most of the systems memory was freed
by the oom-kill of the stress-test.

The utility ends up looping from the rebalance label down through the
wait_iff_congested continiously.  Because order=0,
__alloc_pages_direct_compact skips the call to get_page_from_freelist.
Because all of the reclaimable memory on the system has already been
reclaimed, __alloc_pages_direct_reclaim skips the call to
get_page_from_freelist.  Since there is no __GFP_FS flag, the block with
__alloc_pages_may_oom is skipped.  The loop hits the wait_iff_congested,
then jumps back to rebalance without ever trying to
get_page_from_freelist.  This loop repeats infinitely.

The test case is pretty pathological.  Running a mix of I/O stress-tests
that do a lot of fork() and consume all of the system memory, I can pretty
reliably hit this on 600 nodes, in about 12 hours.  32GB/node.

Signed-off-by: Andrew Barry 
Signed-off-by: Minchan Kim 
Reviewed-by: Rik van Riel
Acked-by: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: page allocator: update free page counters after pages are placed on the free list

2010-09-27T00:21:34+00:00

commit 72853e2991a2702ae93aaf889ac7db743a415dd3 upstream.

When allocating a page, the system uses NR_FREE_PAGES counters to
determine if watermarks would remain intact after the allocation was made.
This check is made without interrupts disabled or the zone lock held and
so is race-prone by nature.  Unfortunately, when pages are being freed in
batch, the counters are updated before the pages are added on the list.
During this window, the counters are misleading as the pages do not exist
yet.  When under significant pressure on systems with large numbers of
CPUs, it's possible for processes to make progress even though they should
have been stalled.  This is particularly problematic if a number of the
processes are using GFP_ATOMIC as the min watermark can be accidentally
breached and in extreme cases, the system can livelock.

This patch updates the counters after the pages have been added to the
list.  This makes the allocator more cautious with respect to preserving
the watermarks and mitigates livelock possibilities.

[akpm@linux-foundation.org: avoid modifying incoming args]
Signed-off-by: Mel Gorman 
Reviewed-by: Rik van Riel 
Reviewed-by: Minchan Kim 
Reviewed-by: KAMEZAWA Hiroyuki 
Reviewed-by: Christoph Lameter 
Reviewed-by: KOSAKI Motohiro 
Acked-by: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: page allocator: calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake

2010-09-27T00:21:34+00:00

commit aa45484031ddee09b06350ab8528bfe5b2c76d1c upstream.

Ordinarily watermark checks are based on the vmstat NR_FREE_PAGES as it is
cheaper than scanning a number of lists.  To avoid synchronization
overhead, counter deltas are maintained on a per-cpu basis and drained
both periodically and when the delta is above a threshold.  On large CPU
systems, the difference between the estimated and real value of
NR_FREE_PAGES can be very high.  If NR_FREE_PAGES is much higher than
number of real free page in buddy, the VM can allocate pages below min
watermark, at worst reducing the real number of pages to zero.  Even if
the OOM killer kills some victim for freeing memory, it may not free
memory if the exit path requires a new page resulting in livelock.

This patch introduces a zone_page_state_snapshot() function (courtesy of
Christoph) that takes a slightly more accurate view of an arbitrary vmstat
counter.  It is used to read NR_FREE_PAGES while kswapd is awake to avoid
the watermark being accidentally broken.  The estimate is not perfect and
may result in cache line bounces but is expected to be lighter than the
IPI calls necessary to continually drain the per-cpu counters while kswapd
is awake.

Signed-off-by: Christoph Lameter 
Signed-off-by: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: page allocator: drain per-cpu lists after direct reclaim allocation fails

2010-09-27T00:21:33+00:00

commit 9ee493ce0a60bf42c0f8fd0b0fe91df5704a1cbf upstream.

When under significant memory pressure, a process enters direct reclaim
and immediately afterwards tries to allocate a page.  If it fails and no
further progress is made, it's possible the system will go OOM.  However,
on systems with large amounts of memory, it's possible that a significant
number of pages are on per-cpu lists and inaccessible to the calling
process.  This leads to a process entering direct reclaim more often than
it should increasing the pressure on the system and compounding the
problem.

This patch notes that if direct reclaim is making progress but allocations
are still failing that the system is already under heavy pressure.  In
this case, it drains the per-cpu lists and tries the allocation a second
time before continuing.

Signed-off-by: Mel Gorman 
Reviewed-by: Minchan Kim 
Reviewed-by: KAMEZAWA Hiroyuki 
Reviewed-by: KOSAKI Motohiro 
Reviewed-by: Christoph Lameter 
Cc: Dave Chinner 
Cc: Wu Fengguang 
Cc: David Rientjes 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: fix migratetype bug which slowed swapping

2010-02-09T12:50:49+00:00

commit a7016235a61d520e6806f38129001d935c4b6661 upstream.

After memory pressure has forced it to dip into the reserves, 2.6.32's
5f8dcc21211a3d4e3a7a5ca366b469fb88117f61 "page-allocator: split per-cpu
list into one-list-per-migrate-type" has been returning MIGRATE_RESERVE
pages to the MIGRATE_MOVABLE free_list: in some sense depleting reserves.

Fix that in the most straightforward way (which, considering the overheads
of alternative approaches, is Mel's preference): the right migratetype is
already in page_private(page), but free_pcppages_bulk() wasn't using it.

How did this bug show up?  As a 20% slowdown in my tmpfs loop kbuild
swapping tests, on PowerMac G5 with SLUB allocator.  Bisecting to that
commit was easy, but explaining the magnitude of the slowdown not easy.

The same effect appears, but much less markedly, with SLAB, and even
less markedly on other machines (the PowerMac divides into fewer zones
than x86, I think that may be a factor).  We guess that lumpy reclaim
of short-lived high-order pages is implicated in some way, and probably
this bug has been tickling a poor decision somewhere in page reclaim.

But instrumentation hasn't told me much, I've run out of time and
imagination to determine exactly what's going on, and shouldn't hold up
the fix any longer: it's valid, and might even fix other misbehaviours.

Signed-off-by: Hugh Dickins 
Acked-by: Mel Gorman 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

page allocator: update NR_FREE_PAGES only when necessary

2010-01-22T23:18:12+00:00

commit 6ccf80eb15ccaca4d3f1ab5162b9ded5eecd9971 upstream.

commit f2260e6b (page allocator: update NR_FREE_PAGES only as necessary)
made one minor regression.  if __rmqueue() was failed, NR_FREE_PAGES stat
go wrong.  this patch fixes it.

Signed-off-by: KOSAKI Motohiro 
Cc: Mel Gorman 
Reviewed-by: Minchan Kim 
Reported-by: Huang Shijie 
Reviewed-by: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

page allocator: Do not allow interrupts to use ALLOC_HARDER

2009-11-12T15:25:56+00:00

Commit 341ce06f69abfafa31b9468410a13dbd60e2b237 ("page allocator:
calculate the alloc_flags for allocation only once") altered watermark
logic slightly by allowing rt_tasks that are handling an interrupt to set
ALLOC_HARDER.  This patch brings the watermark logic more in line with
2.6.30.

This change results in a reduction of the number high-order GFP_ATOMIC
allocation failures reported.  See
http://www.gossamer-threads.com/lists/linux/kernel/1144153

[rientjes@google.com: Spotted the problem]
Signed-off-by: Mel Gorman 
Reviewed-by: Pekka Enberg 
Reviewed-by: Rik van Riel 
Reviewed-by: KOSAKI Motohiro 
Cc: David Rientjes 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

page allocator: always wake kswapd when restarting an allocation attempt after direct reclaim failed

2009-11-12T15:25:56+00:00

If a direct reclaim makes no forward progress, it considers whether it
should go OOM or not.  Whether OOM is triggered or not, it may retry the
allocation afterwards.  In times past, this would always wake kswapd as
well but currently, kswapd is not woken up after direct reclaim fails.
For order-0 allocations, this makes little difference but if there is a
heavy mix of higher-order allocations that direct reclaim is failing for,
it might mean that kswapd is not rewoken for higher orders as much as it
did previously.

This patch wakes up kswapd when an allocation is being retried after a
direct reclaim failure.  It would be expected that kswapd is already
awake, but this has the effect of telling kswapd to reclaim at the higher
order as well.

Signed-off-by: Mel Gorman 
Reviewed-by: Christoph Lameter 
Reviewed-by: Pekka Enberg 
Reviewed-by: KOSAKI Motohiro 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

revert "mm: oom analysis: add buffer cache information to show_free_areas()"

2009-10-29T14:39:27+00:00

Revert

    commit 71de1ccbe1fb40203edd3beb473f8580d917d2ca
    Author:     KOSAKI Motohiro 
    AuthorDate: Mon Sep 21 17:01:31 2009 -0700
    Commit:     Linus Torvalds 
    CommitDate: Tue Sep 22 07:17:27 2009 -0700

        mm: oom analysis: add buffer cache information to show_free_areas()

show_free_areas() is called during page allocation failures, and page
allocation failures can occur in any calling context.

But nr_blockdev_pages() takes VFS locks which should not be taken from
hard IRQ context (at least).  The result is lockdep warnings (and
deadlockability) during page allocation failures.

Cc: KOSAKI Motohiro 
Cc: Wu Fengguang 
Cc: Rik van Riel 
Cc: David Rientjes 
Cc: Alexey Dobriyan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'hwpoison' of git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6

2009-09-24T14:53:22+00:00

* 'hwpoison' of git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6: (21 commits)
  HWPOISON: Enable error_remove_page on btrfs
  HWPOISON: Add simple debugfs interface to inject hwpoison on arbitary PFNs
  HWPOISON: Add madvise() based injector for hardware poisoned pages v4
  HWPOISON: Enable error_remove_page for NFS
  HWPOISON: Enable .remove_error_page for migration aware file systems
  HWPOISON: The high level memory error handler in the VM v7
  HWPOISON: Add PR_MCE_KILL prctl to control early kill behaviour per process
  HWPOISON: shmem: call set_page_dirty() with locked page
  HWPOISON: Define a new error_remove_page address space op for async truncation
  HWPOISON: Add invalidate_inode_page
  HWPOISON: Refactor truncate to allow direct truncating of page v2
  HWPOISON: check and isolate corrupted free pages v2
  HWPOISON: Handle hardware poisoned pages in try_to_unmap
  HWPOISON: Use bitmask/action code for try_to_unmap behaviour
  HWPOISON: x86: Add VM_FAULT_HWPOISON handling to x86 page fault handler v2
  HWPOISON: Add poison check to page fault handling
  HWPOISON: Add basic support for poisoned pages in fault handler v3
  HWPOISON: Add new SIGBUS error codes for hardware poison signals
  HWPOISON: Add support for poison swap entries v2
  HWPOISON: Export some rmap vma locking to outside world
  ...