linux-toradex.git/mm/vmscan.c, branch v4.10

mm, memcg: fix the active list aging for lowmem requests when memcg is enabled

2017-01-11T02:31:55+00:00

Nils Holland and Klaus Ethgen have reported unexpected OOM killer
invocations with 32b kernel starting with 4.8 kernels

	kworker/u4:5 invoked oom-killer: gfp_mask=0x2400840(GFP_NOFS|__GFP_NOFAIL), nodemask=0, order=0, oom_score_adj=0
	kworker/u4:5 cpuset=/ mems_allowed=0
	CPU: 1 PID: 2603 Comm: kworker/u4:5 Not tainted 4.9.0-gentoo #2
	[...]
	Mem-Info:
	active_anon:58685 inactive_anon:90 isolated_anon:0
	 active_file:274324 inactive_file:281962 isolated_file:0
	 unevictable:0 dirty:649 writeback:0 unstable:0
	 slab_reclaimable:40662 slab_unreclaimable:17754
	 mapped:7382 shmem:202 pagetables:351 bounce:0
	 free:206736 free_pcp:332 free_cma:0
	Node 0 active_anon:234740kB inactive_anon:360kB active_file:1097296kB inactive_file:1127848kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:29528kB dirty:2596kB writeback:0kB shmem:0kB shmem_thp: 0kB shmem_pmdmapped: 184320kB anon_thp: 808kB writeback_tmp:0kB unstable:0kB pages_scanned:0 all_unreclaimable? no
	DMA free:3952kB min:788kB low:984kB high:1180kB active_anon:0kB inactive_anon:0kB active_file:7316kB inactive_file:0kB unevictable:0kB writepending:96kB present:15992kB managed:15916kB mlocked:0kB slab_reclaimable:3200kB slab_unreclaimable:1408kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
	lowmem_reserve[]: 0 813 3474 3474
	Normal free:41332kB min:41368kB low:51708kB high:62048kB active_anon:0kB inactive_anon:0kB active_file:532748kB inactive_file:44kB unevictable:0kB writepending:24kB present:897016kB managed:836248kB mlocked:0kB slab_reclaimable:159448kB slab_unreclaimable:69608kB kernel_stack:1112kB pagetables:1404kB bounce:0kB free_pcp:528kB local_pcp:340kB free_cma:0kB
	lowmem_reserve[]: 0 0 21292 21292
	HighMem free:781660kB min:512kB low:34356kB high:68200kB active_anon:234740kB inactive_anon:360kB active_file:557232kB inactive_file:1127804kB unevictable:0kB writepending:2592kB present:2725384kB managed:2725384kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:800kB local_pcp:608kB free_cma:0kB

the oom killer is clearly pre-mature because there there is still a lot
of page cache in the zone Normal which should satisfy this lowmem
request.  Further debugging has shown that the reclaim cannot make any
forward progress because the page cache is hidden in the active list
which doesn't get rotated because inactive_list_is_low is not memcg
aware.

The code simply subtracts per-zone highmem counters from the respective
memcg's lru sizes which doesn't make any sense.  We can simply end up
always seeing the resulting active and inactive counts 0 and return
false.  This issue is not limited to 32b kernels but in practice the
effect on systems without CONFIG_HIGHMEM would be much harder to notice
because we do not invoke the OOM killer for allocations requests
targeting < ZONE_NORMAL.

Fix the issue by tracking per zone lru page counts in mem_cgroup_per_node
and subtract per-memcg highmem counts when memcg is enabled.  Introduce
helper lruvec_zone_lru_size which redirects to either zone counters or
mem_cgroup_get_zone_lru_size when appropriate.

We are losing empty LRU but non-zero lru size detection introduced by
ca707239e8a7 ("mm: update_lru_size warn and reset bad lru_size") because
of the inherent zone vs. node discrepancy.

Fixes: f8d1a31163fc ("mm: consider whether to decivate based on eligible zones inactive ratio")
Link: http://lkml.kernel.org/r/20170104100825.3729-1-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Reported-by: Nils Holland 
Tested-by: Nils Holland 
Reported-by: Klaus Ethgen 
Acked-by: Minchan Kim 
Acked-by: Mel Gorman 
Acked-by: Johannes Weiner 
Reviewed-by: Vladimir Davydov 
Cc: 	[4.8+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'akpm' (patches from Andrew)

2016-12-13T04:50:02+00:00

Merge updates from Andrew Morton:

 - various misc bits

 - most of MM (quite a lot of MM material is awaiting the merge of
   linux-next dependencies)

 - kasan

 - printk updates

 - procfs updates

 - MAINTAINERS

 - /lib updates

 - checkpatch updates

* emailed patches from Andrew Morton : (123 commits)
  init: reduce rootwait polling interval time to 5ms
  binfmt_elf: use vmalloc() for allocation of vma_filesz
  checkpatch: don't emit unified-diff error for rename-only patches
  checkpatch: don't check c99 types like uint8_t under tools
  checkpatch: avoid multiple line dereferences
  checkpatch: don't check .pl files, improve absolute path commit log test
  scripts/checkpatch.pl: fix spelling
  checkpatch: don't try to get maintained status when --no-tree is given
  lib/ida: document locking requirements a bit better
  lib/rbtree.c: fix typo in comment of ____rb_erase_color
  lib/Kconfig.debug: make CONFIG_STRICT_DEVMEM depend on CONFIG_DEVMEM
  MAINTAINERS: add drm and drm/i915 irc channels
  MAINTAINERS: add "C:" for URI for chat where developers hang out
  MAINTAINERS: add drm and drm/i915 bug filing info
  MAINTAINERS: add "B:" for URI where to file bugs
  get_maintainer: look for arbitrary letter prefixes in sections
  printk: add Kconfig option to set default console loglevel
  printk/sound: handle more message headers
  printk/btrfs: handle more message headers
  printk/kdb: handle more message headers
  ...

Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2016-12-13T03:25:04+00:00

Pull smp hotplug updates from Thomas Gleixner:
 "This is the final round of converting the notifier mess to the state
  machine. The removal of the notifiers and the related infrastructure
  will happen around rc1, as there are conversions outstanding in other
  trees.

  The whole exercise removed about 2000 lines of code in total and in
  course of the conversion several dozen bugs got fixed. The new
  mechanism allows to test almost every hotplug step standalone, so
  usage sites can exercise all transitions extensively.

  There is more room for improvement, like integrating all the
  pointlessly different architecture mechanisms of synchronizing,
  setting cpus online etc into the core code"

* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (60 commits)
  tracing/rb: Init the CPU mask on allocation
  soc/fsl/qbman: Convert to hotplug state machine
  soc/fsl/qbman: Convert to hotplug state machine
  zram: Convert to hotplug state machine
  KVM/PPC/Book3S HV: Convert to hotplug state machine
  arm64/cpuinfo: Convert to hotplug state machine
  arm64/cpuinfo: Make hotplug notifier symmetric
  mm/compaction: Convert to hotplug state machine
  iommu/vt-d: Convert to hotplug state machine
  mm/zswap: Convert pool to hotplug state machine
  mm/zswap: Convert dst-mem to hotplug state machine
  mm/zsmalloc: Convert to hotplug state machine
  mm/vmstat: Convert to hotplug state machine
  mm/vmstat: Avoid on each online CPU loops
  mm/vmstat: Drop get_online_cpus() from init_cpu_node_state/vmstat_cpu_dead()
  tracing/rb: Convert to hotplug state machine
  oprofile/nmi timer: Convert to hotplug state machine
  net/iucv: Use explicit clean up labels in iucv_init()
  x86/pci/amd-bus: Convert to hotplug state machine
  x86/oprofile/nmi: Convert to hotplug state machine
  ...

mm/vmscan.c: set correct defer count for shrinker

2016-12-13T02:55:07+00:00

Our system uses significantly more slab memory with memcg enabled with
the latest kernel.  With 3.10 kernel, slab uses 2G memory, while with
4.6 kernel, 6G memory is used.  The shrinker has problem.  Let's see we
have two memcg for one shrinker.  In do_shrink_slab:

1. Check cg1.  nr_deferred = 0, assume total_scan = 700.  batch size
   is 1024, then no memory is freed.  nr_deferred = 700

2. Check cg2.  nr_deferred = 700.  Assume freeable = 20, then
   total_scan = 10 or 40.  Let's assume it's 10.  No memory is freed.
   nr_deferred = 10.

The deferred share of cg1 is lost in this case.  kswapd will free no
memory even run above steps again and again.

The fix makes sure one memcg's deferred share isn't lost.

Link: http://lkml.kernel.org/r/2414be961b5d25892060315fbb56bb19d81d0c07.1476227351.git.shli@fb.com
Signed-off-by: Shaohua Li 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Vladimir Davydov 
Cc: 	[4.0+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, vmscan: add cond_resched() into shrink_node_memcg()

2016-12-03T02:48:03+00:00

Boris Zhmurov has reported RCU stalls during the kswapd reclaim:

  INFO: rcu_sched detected stalls on CPUs/tasks:
   23-...: (22 ticks this GP) idle=92f/140000000000000/0 softirq=2638404/2638404 fqs=23
   (detected by 4, t=6389 jiffies, g=786259, c=786258, q=42115)
  Task dump for CPU 23:
  kswapd1         R  running task        0   148      2 0x00000008
  Call Trace:
    shrink_node+0xd2/0x2f0
    kswapd+0x2cb/0x6a0
    mem_cgroup_shrink_node+0x160/0x160
    kthread+0xbd/0xe0
    __switch_to+0x1fa/0x5c0
    ret_from_fork+0x1f/0x40
    kthread_create_on_node+0x180/0x180

a closer code inspection has shown that we might indeed miss all the
scheduling points in the reclaim path if no pages can be isolated from
the LRU list.  This is a pathological case but other reports from Donald
Buczek have shown that we might indeed hit such a path:

        clusterd-989   [009] .... 118023.654491: mm_vmscan_direct_reclaim_end: nr_reclaimed=193
         kswapd1-86    [001] dN.. 118023.987475: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239830 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118024.320968: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239844 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118024.654375: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239858 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118024.987036: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239872 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118025.319651: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239886 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118025.652248: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239900 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118025.984870: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239914 nr_taken=0 file=1
  [...]
         kswapd1-86    [001] dN.. 118084.274403: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4241133 nr_taken=0 file=1

this is minute long snapshot which didn't take a single page from the
LRU.  It is not entirely clear why only 1303 pages have been scanned
during that time (maybe there was a heavy IRQ activity interfering).

In any case it looks like we can really hit long periods without
scheduling on non preemptive kernels so an explicit cond_resched() in
shrink_node_memcg which is independent on the reclaim operation is due.

Link: http://lkml.kernel.org/r/20161202095841.16648-1-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Reported-by: Boris Zhmurov 
Tested-by: Boris Zhmurov 
Reported-by: Donald Buczek 
Reported-by: "Christopher S. Aker" 
Reported-by: Paul Menzel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/vmscan: Convert to hotplug state machine

2016-11-09T22:45:27+00:00

Install the callbacks via the state machine.

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Thomas Gleixner 
Cc: linux-mm@kvack.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20161103145021.28528-8-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner

mm: memcontrol: do not recurse in direct reclaim

2016-10-28T01:43:43+00:00

On 4.0, we saw a stack corruption from a page fault entering direct
memory cgroup reclaim, calling into btrfs_releasepage(), which then
tried to allocate an extent and recursed back into a kmem charge ad
nauseam:

  [...]
  btrfs_releasepage+0x2c/0x30
  try_to_release_page+0x32/0x50
  shrink_page_list+0x6da/0x7a0
  shrink_inactive_list+0x1e5/0x510
  shrink_lruvec+0x605/0x7f0
  shrink_zone+0xee/0x320
  do_try_to_free_pages+0x174/0x440
  try_to_free_mem_cgroup_pages+0xa7/0x130
  try_charge+0x17b/0x830
  memcg_charge_kmem+0x40/0x80
  new_slab+0x2d9/0x5a0
  __slab_alloc+0x2fd/0x44f
  kmem_cache_alloc+0x193/0x1e0
  alloc_extent_state+0x21/0xc0
  __clear_extent_bit+0x2b5/0x400
  try_release_extent_mapping+0x1a3/0x220
  __btrfs_releasepage+0x31/0x70
  btrfs_releasepage+0x2c/0x30
  try_to_release_page+0x32/0x50
  shrink_page_list+0x6da/0x7a0
  shrink_inactive_list+0x1e5/0x510
  shrink_lruvec+0x605/0x7f0
  shrink_zone+0xee/0x320
  do_try_to_free_pages+0x174/0x440
  try_to_free_mem_cgroup_pages+0xa7/0x130
  try_charge+0x17b/0x830
  mem_cgroup_try_charge+0x65/0x1c0
  handle_mm_fault+0x117f/0x1510
  __do_page_fault+0x177/0x420
  do_page_fault+0xc/0x10
  page_fault+0x22/0x30

On later kernels, kmem charging is opt-in rather than opt-out, and that
particular kmem allocation in btrfs_releasepage() is no longer being
charged and won't recurse and overrun the stack anymore.

But it's not impossible for an accounted allocation to happen from the
memcg direct reclaim context, and we needed to reproduce this crash many
times before we even got a useful stack trace out of it.

Like other direct reclaimers, mark tasks in memcg reclaim PF_MEMALLOC to
avoid recursing into any other form of direct reclaim.  Then let
recursive charges from PF_MEMALLOC contexts bypass the cgroup limit.

Link: http://lkml.kernel.org/r/20161025141050.GA13019@cmpxchg.org
Signed-off-by: Johannes Weiner 
Acked-by: Michal Hocko 
Cc: Vladimir Davydov 
Cc: Tejun Heo 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: use zonelist name instead of using hardcoded index

2016-10-08T01:46:28+00:00

Use the existing enums instead of hardcoded index when looking at the
zonelist.  This makes it more readable.  No functionality change by this
patch.

Link: http://lkml.kernel.org/r/1472227078-24852-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com
Signed-off-by: Aneesh Kumar K.V 
Reviewed-by: Anshuman Khandual 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, vmscan: get rid of throttle_vm_writeout

2016-10-08T01:46:27+00:00

throttle_vm_writeout() was introduced back in 2005 to fix OOMs caused by
excessive pageout activity during the reclaim.  Too many pages could be
put under writeback therefore LRUs would be full of unreclaimable pages
until the IO completes and in turn the OOM killer could be invoked.

There have been some important changes introduced since then in the
reclaim path though.  Writers are throttled by balance_dirty_pages when
initiating the buffered IO and later during the memory pressure, the
direct reclaim is throttled by wait_iff_congested if the node is
considered congested by dirty pages on LRUs and the underlying bdi is
congested by the queued IO.  The kswapd is throttled as well if it
encounters pages marked for immediate reclaim or under writeback which
signals that that there are too many pages under writeback already.
Finally should_reclaim_retry does congestion_wait if the reclaim cannot
make any progress and there are too many dirty/writeback pages.

Another important aspect is that we do not issue any IO from the direct
reclaim context anymore.  In a heavy parallel load this could queue a
lot of IO which would be very scattered and thus unefficient which would
just make the problem worse.

This three mechanisms should throttle and keep the amount of IO in a
steady state even under heavy IO and memory pressure so yet another
throttling point doesn't really seem helpful.  Quite contrary, Mikulas
Patocka has reported that swap backed by dm-crypt doesn't work properly
because the swapout IO cannot make sufficient progress as the writeout
path depends on dm_crypt worker which has to allocate memory to perform
the encryption.  In order to guarantee a forward progress it relies on
the mempool allocator.  mempool_alloc(), however, prefers to use the
underlying (usually page) allocator before it grabs objects from the
pool.  Such an allocation can dive into the memory reclaim and
consequently to throttle_vm_writeout.  If there are too many dirty or
pages under writeback it will get throttled even though it is in fact a
flusher to clear pending pages.

  kworker/u4:0    D ffff88003df7f438 10488     6      2	0x00000000
  Workqueue: kcryptd kcryptd_crypt [dm_crypt]
  Call Trace:
    schedule+0x3c/0x90
    schedule_timeout+0x1d8/0x360
    io_schedule_timeout+0xa4/0x110
    congestion_wait+0x86/0x1f0
    throttle_vm_writeout+0x44/0xd0
    shrink_zone_memcg+0x613/0x720
    shrink_zone+0xe0/0x300
    do_try_to_free_pages+0x1ad/0x450
    try_to_free_pages+0xef/0x300
    __alloc_pages_nodemask+0x879/0x1210
    alloc_pages_current+0xa1/0x1f0
    new_slab+0x2d7/0x6a0
    ___slab_alloc+0x3fb/0x5c0
    __slab_alloc+0x51/0x90
    kmem_cache_alloc+0x27b/0x310
    mempool_alloc_slab+0x1d/0x30
    mempool_alloc+0x91/0x230
    bio_alloc_bioset+0xbd/0x260
    kcryptd_crypt+0x114/0x3b0 [dm_crypt]

Let's just drop throttle_vm_writeout altogether.  It is not very much
helpful anymore.

I have tried to test a potential writeback IO runaway similar to the one
described in the original patch which has introduced that [1].  Small
virtual machine (512MB RAM, 4 CPUs, 2G of swap space and disk image on a
rather slow NFS in a sync mode on the host) with 8 parallel writers each
writing 1G worth of data.  As soon as the pagecache fills up and the
direct reclaim hits then I start anon memory consumer in a loop
(allocating 300M and exiting after populating it) in the background to
make the memory pressure even stronger as well as to disrupt the steady
state for the IO.  The direct reclaim is throttled because of the
congestion as well as kswapd hitting congestion_wait due to nr_immediate
but throttle_vm_writeout doesn't ever trigger the sleep throughout the
test.  Dirty+writeback are close to nr_dirty_threshold with some
fluctuations caused by the anon consumer.

[1] https://www2.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.9-rc1/2.6.9-rc1-mm3/broken-out/vm-pageout-throttling.patch
Link: http://lkml.kernel.org/r/1471171473-21418-1-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Reported-by: Mikulas Patocka 
Cc: Marcelo Tosatti 
Cc: NeilBrown 
Cc: Ondrej Kozina 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, vmscan: make compaction_ready() more accurate and readable

2016-10-08T01:46:27+00:00

The compaction_ready() is used during direct reclaim for costly order
allocations to skip reclaim for zones where compaction should be
attempted instead.  It's combining the standard compaction_suitable()
check with its own watermark check based on high watermark with extra
gap, and the result is confusing at best.

This patch attempts to better structure and document the checks
involved.  First, compaction_suitable() can determine that the
allocation should either succeed already, or that compaction doesn't
have enough free pages to proceed.  The third possibility is that
compaction has enough free pages, but we still decide to reclaim first -
unless we are already above the high watermark with gap.  This does not
mean that the reclaim will actually reach this watermark during single
attempt, this is rather an over-reclaim protection.  So document the
code as such.  The check for compaction_deferred() is removed
completely, as it in fact had no proper role here.

The result after this patch is mainly a less confusing code.  We also
skip some over-reclaim in cases where the allocation should already
succed.

Link: http://lkml.kernel.org/r/20160810091226.6709-12-vbabka@suse.cz
Signed-off-by: Vlastimil Babka 
Tested-by: Lorenzo Stoakes 
Acked-by: Michal Hocko 
Cc: Mel Gorman 
Cc: Joonsoo Kim 
Cc: David Rientjes 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds