Andrew has noticed some inconsistencies in oom_reap_task_mm. Notably
- Undocumented return value.
- comment "failed to reap part..." is misleading - sounds like it's
referring to something which happened in the past, is in fact
referring to something which might happen in the future.
- fails to call trace_finish_task_reaping() in one case
- code duplication.
- Increases mmap_sem hold time a little by moving
trace_finish_task_reaping() inside the locked region. So sue me ;)
- Sharing the finish: path means that the trace event won't
distinguish between the two sources of finishing.
Add a short explanation for the return value and fix the rest by
reorganizing the function a bit to have unified function exit paths.
Link: http://lkml.kernel.org/r/20180724141747.GP28386@dhcp22.suse.cz
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The default page memory unit of OOM task dump events might not be
intuitive and potentially misleading for the non-initiated when debugging
OOM events: These are pages and not kBs. Add a small printk prior to the
task dump informing that the memory units are actually memory _pages_.
Also extends PID field to align on up to 7 characters.
Reference https://lkml.org/lkml/2018/7/3/1201
Link: http://lkml.kernel.org/r/c795eb5129149ed8a6345c273aba167ff1bbd388.1530715938.git.rfreire@redhat.com
Signed-off-by: Rodrigo Freire <rfreire@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
oom_reaper used to rely on the oom_lock since e2fe14564d ("oom_reaper:
close race with exiting task"). We do not really need the lock anymore
though. 2129258024 ("mm: oom: let oom_reap_task and exit_mmap run
concurrently") has removed serialization with the exit path based on the
mm reference count and so we do not really rely on the oom_lock anymore.
Tetsuo was arguing that at least MMF_OOM_SKIP should be set under the lock
to prevent from races when the page allocator didn't manage to get the
freed (reaped) memory in __alloc_pages_may_oom but it sees the flag later
on and move on to another victim. Although this is possible in principle
let's wait for it to actually happen in real life before we make the
locking more complex again.
Therefore remove the oom_lock for oom_reaper paths (both exit_mmap and
oom_reap_task_mm). The reaper serializes with exit_mmap by mmap_sem +
MMF_OOM_SKIP flag. There is no synchronization with out_of_memory path
now.
[mhocko@kernel.org: oom_reap_task_mm should return false when __oom_reap_task_mm did]
Link: http://lkml.kernel.org/r/20180724141747.GP28386@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/20180719075922.13784-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Suggested-by: David Rientjes <rientjes@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There are several blockable mmu notifiers which might sleep in
mmu_notifier_invalidate_range_start and that is a problem for the
oom_reaper because it needs to guarantee a forward progress so it cannot
depend on any sleepable locks.
Currently we simply back off and mark an oom victim with blockable mmu
notifiers as done after a short sleep. That can result in selecting a new
oom victim prematurely because the previous one still hasn't torn its
memory down yet.
We can do much better though. Even if mmu notifiers use sleepable locks
there is no reason to automatically assume those locks are held. Moreover
majority of notifiers only care about a portion of the address space and
there is absolutely zero reason to fail when we are unmapping an unrelated
range. Many notifiers do really block and wait for HW which is harder to
handle and we have to bail out though.
This patch handles the low hanging fruit.
__mmu_notifier_invalidate_range_start gets a blockable flag and callbacks
are not allowed to sleep if the flag is set to false. This is achieved by
using trylock instead of the sleepable lock for most callbacks and
continue as long as we do not block down the call chain.
I think we can improve that even further because there is a common pattern
to do a range lookup first and then do something about that. The first
part can be done without a sleeping lock in most cases AFAICS.
The oom_reaper end then simply retries if there is at least one notifier
which couldn't make any progress in !blockable mode. A retry loop is
already implemented to wait for the mmap_sem and this is basically the
same thing.
The simplest way for driver developers to test this code path is to wrap
userspace code which uses these notifiers into a memcg and set the hard
limit to hit the oom. This can be done e.g. after the test faults in all
the mmu notifier managed memory and set the hard limit to something really
small. Then we are looking for a proper process tear down.
[akpm@linux-foundation.org: coding style fixes]
[akpm@linux-foundation.org: minor code simplification]
Link: http://lkml.kernel.org/r/20180716115058.5559-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Christian König <christian.koenig@amd.com> # AMD notifiers
Acked-by: Leon Romanovsky <leonro@mellanox.com> # mlx and umem_odp
Reported-by: David Rientjes <rientjes@google.com>
Cc: "David (ChunMing) Zhou" <David1.Zhou@amd.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: Dennis Dalessandro <dennis.dalessandro@intel.com>
Cc: Sudeep Dutt <sudeep.dutt@intel.com>
Cc: Ashutosh Dixit <ashutosh.dixit@intel.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Tetsuo has pointed out that since 27ae357fa8 ("mm, oom: fix concurrent
munlock and oom reaper unmap, v3") we have a strong synchronization
between the oom_killer and victim's exiting because both have to take
the oom_lock. Therefore the original heuristic to sleep for a short
time in out_of_memory doesn't serve the original purpose.
Moreover Tetsuo has noticed that the short sleep can be more harmful
than actually useful. Hammering the system with many processes can lead
to a starvation when the task holding the oom_lock can block for a long
time (minutes) and block any further progress because the oom_reaper
depends on the oom_lock as well.
Drop the short sleep from out_of_memory when we hold the lock. Keep the
sleep when the trylock fails to throttle the concurrent OOM paths a bit.
This should be solved in a more reasonable way (e.g. sleep proportional
to the time spent in the active reclaiming etc.) but this is much more
complex thing to achieve. This is a quick fixup to remove a stale code.
Link: http://lkml.kernel.org/r/20180709074706.30635-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Andrew Morton <akpm@linux-foundation.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>
Commit e27be240df ("mm: memcg: make sure memory.events is uptodate
when waking pollers") converted most of memcg event counters to
per-memcg atomics, which made them less confusing for a user. The
"oom_kill" counter remained untouched, so now it behaves differently
than other counters (including "oom"). This adds nothing but confusion.
Let's fix this by adding the MEMCG_OOM_KILL event, and follow the
MEMCG_OOM approach.
This also removes a hack from count_memcg_event_mm(), introduced earlier
specially for the OOM_KILL counter.
[akpm@linux-foundation.org: fix for droppage of memcg-replace-mm-owner-with-mm-memcg.patch]
Link: http://lkml.kernel.org/r/20180508124637.29984-1-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
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>
This patch renames struct page_counter fields:
count -> usage
limit -> max
and the corresponding functions:
page_counter_limit() -> page_counter_set_max()
mem_cgroup_get_limit() -> mem_cgroup_get_max()
mem_cgroup_resize_limit() -> mem_cgroup_resize_max()
memcg_update_kmem_limit() -> memcg_update_kmem_max()
memcg_update_tcp_limit() -> memcg_update_tcp_max()
The idea behind this renaming is to have the direct matching
between memory cgroup knobs (low, high, max) and page_counters API.
This is pure renaming, this patch doesn't bring any functional change.
Link: http://lkml.kernel.org/r/20180405185921.4942-1-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since exit_mmap() is done without the protection of mm->mmap_sem, it is
possible for the oom reaper to concurrently operate on an mm until
MMF_OOM_SKIP is set.
This allows munlock_vma_pages_all() to concurrently run while the oom
reaper is operating on a vma. Since munlock_vma_pages_range() depends
on clearing VM_LOCKED from vm_flags before actually doing the munlock to
determine if any other vmas are locking the same memory, the check for
VM_LOCKED in the oom reaper is racy.
This is especially noticeable on architectures such as powerpc where
clearing a huge pmd requires serialize_against_pte_lookup(). If the pmd
is zapped by the oom reaper during follow_page_mask() after the check
for pmd_none() is bypassed, this ends up deferencing a NULL ptl or a
kernel oops.
Fix this by manually freeing all possible memory from the mm before
doing the munlock and then setting MMF_OOM_SKIP. The oom reaper can not
run on the mm anymore so the munlock is safe to do in exit_mmap(). It
also matches the logic that the oom reaper currently uses for
determining when to set MMF_OOM_SKIP itself, so there's no new risk of
excessive oom killing.
This issue fixes CVE-2018-1000200.
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1804241526320.238665@chino.kir.corp.google.com
Fixes: 2129258024 ("mm: oom: let oom_reap_task and exit_mmap run concurrently")
Signed-off-by: David Rientjes <rientjes@google.com>
Suggested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org> [4.14+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I got "oom_reaper: unable to reap pid:" messages when the victim thread
was blocked inside free_pgtables() (which occurred after returning from
unmap_vmas() and setting MMF_OOM_SKIP). We don't need to complain when
exit_mmap() already set MMF_OOM_SKIP.
Killed process 7558 (a.out) total-vm:4176kB, anon-rss:84kB, file-rss:0kB, shmem-rss:0kB
oom_reaper: unable to reap pid:7558 (a.out)
a.out D13272 7558 6931 0x00100084
Call Trace:
schedule+0x2d/0x80
rwsem_down_write_failed+0x2bb/0x440
call_rwsem_down_write_failed+0x13/0x20
down_write+0x49/0x60
unlink_file_vma+0x28/0x50
free_pgtables+0x36/0x100
exit_mmap+0xbb/0x180
mmput+0x50/0x110
copy_process.part.41+0xb61/0x1fe0
_do_fork+0xe6/0x560
do_syscall_64+0x74/0x230
entry_SYSCALL_64_after_hwframe+0x42/0xb7
Link: http://lkml.kernel.org/r/201803221946.DHG65638.VFJHFtOSQLOMOF@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since the 2.6 kernel, the oom killer has slightly biased away from
CAP_SYS_ADMIN processes by discounting some of its memory usage in
comparison to other processes.
This has always been implicit and nothing exactly relies on the
behavior.
Gaurav notices that __task_cred() can dereference a potentially freed
pointer if the task under consideration is exiting because a reference
to the task_struct is not held.
Remove the CAP_SYS_ADMIN bias so that all processes are treated equally.
If any CAP_SYS_ADMIN process would like to be biased against, it is
always allowed to adjust /proc/pid/oom_score_adj.
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1803071548510.6996@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Reported-by: Gaurav Kohli <gkohli@codeaurora.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This uses the new annotation to determine if an mm has mmu notifiers
with blockable invalidate range callbacks to avoid oom reaping.
Otherwise, the callbacks are used around unmap_page_range().
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1712141330120.74052@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Dimitri Sivanich <sivanich@hpe.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Oded Gabbay <oded.gabbay@gmail.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: Sean Hefty <sean.hefty@intel.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
David Rientjes has reported the following memory corruption while the
oom reaper tries to unmap the victims address space
BUG: Bad page map in process oom_reaper pte:6353826300000000 pmd:00000000
addr:00007f50cab1d000 vm_flags:08100073 anon_vma:ffff9eea335603f0 mapping: (null) index:7f50cab1d
file: (null) fault: (null) mmap: (null) readpage: (null)
CPU: 2 PID: 1001 Comm: oom_reaper
Call Trace:
unmap_page_range+0x1068/0x1130
__oom_reap_task_mm+0xd5/0x16b
oom_reaper+0xff/0x14c
kthread+0xc1/0xe0
Tetsuo Handa has noticed that the synchronization inside exit_mmap is
insufficient. We only synchronize with the oom reaper if
tsk_is_oom_victim which is not true if the final __mmput is called from
a different context than the oom victim exit path. This can trivially
happen from context of any task which has grabbed mm reference (e.g. to
read /proc/<pid>/ file which requires mm etc.).
The race would look like this
oom_reaper oom_victim task
mmget_not_zero
do_exit
mmput
__oom_reap_task_mm mmput
__mmput
exit_mmap
remove_vma
unmap_page_range
Fix this issue by providing a new mm_is_oom_victim() helper which
operates on the mm struct rather than a task. Any context which
operates on a remote mm struct should use this helper in place of
tsk_is_oom_victim. The flag is set in mark_oom_victim and never cleared
so it is stable in the exit_mmap path.
Debugged by Tetsuo Handa.
Link: http://lkml.kernel.org/r/20171210095130.17110-1-mhocko@kernel.org
Fixes: 2129258024 ("mm: oom: let oom_reap_task and exit_mmap run concurrently")
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: David Rientjes <rientjes@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Andrea Argangeli <andrea@kernel.org>
Cc: <stable@vger.kernel.org> [4.14]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
tlb_gather_mmu(&tlb, mm, 0, -1) means gathering the whole virtual memory
space. In this case, tlb->fullmm is true. Some archs like arm64
doesn't flush TLB when tlb->fullmm is true:
commit 5a7862e830 ("arm64: tlbflush: avoid flushing when fullmm == 1").
Which causes leaking of tlb entries.
Will clarifies his patch:
"Basically, we tag each address space with an ASID (PCID on x86) which
is resident in the TLB. This means we can elide TLB invalidation when
pulling down a full mm because we won't ever assign that ASID to
another mm without doing TLB invalidation elsewhere (which actually
just nukes the whole TLB).
I think that means that we could potentially not fault on a kernel
uaccess, because we could hit in the TLB"
There could be a window between complete_signal() sending IPI to other
cores and all threads sharing this mm are really kicked off from cores.
In this window, the oom reaper may calls tlb_flush_mmu_tlbonly() to
flush TLB then frees pages. However, due to the above problem, the TLB
entries are not really flushed on arm64. Other threads are possible to
access these pages through TLB entries. Moreover, a copy_to_user() can
also write to these pages without generating page fault, causes
use-after-free bugs.
This patch gathers each vma instead of gathering full vm space. In this
case tlb->fullmm is not true. The behavior of oom reaper become similar
to munmapping before do_exit, which should be safe for all archs.
Link: http://lkml.kernel.org/r/20171107095453.179940-1-wangnan0@huawei.com
Fixes: aac4536355 ("mm, oom: introduce oom reaper")
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Bob Liu <liubo95@huawei.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
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>
alloc_warn() and dump_header() have to explicitly handle NULL nodemask
which forces both paths to use pr_cont. We can do better. printk
already handles NULL pointers properly so all we need is to teach
nodemask_pr_args to handle NULL nodemask carefully. This allows
simplification of both alloc_warn() and dump_header() and gets rid of
pr_cont altogether.
This patch has been motivated by patch from Joe Perches
http://lkml.kernel.org/r/b31236dfe3fc924054fd7842bde678e71d193638.1509991345.git.joe@perches.com
[akpm@linux-foundation.org: fix tile warning, per Arnd]
Link: http://lkml.kernel.org/r/20171109100531.3cn2hcqnuj7mjaju@dhcp22.suse.cz
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Joe Perches <joe@perches.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since oom_init() is called before userspace processes start, memory
allocation failure for creating the OOM reaper kernel thread will let
the OOM killer call panic() rather than wake up the OOM reaper.
Link: http://lkml.kernel.org/r/1510137800-4602-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently, we account page tables separately for each page table level,
but that's redundant -- we only make use of total memory allocated to
page tables for oom_badness calculation. We also provide the
information to userspace, but it has dubious value there too.
This patch switches page table accounting to single counter.
mm->pgtables_bytes is now used to account all page table levels. We use
bytes, because page table size for different levels of page table tree
may be different.
The change has user-visible effect: we don't have VmPMD and VmPUD
reported in /proc/[pid]/status. Not sure if anybody uses them. (As
alternative, we can always report 0 kB for them.)
OOM-killer report is also slightly changed: we now report pgtables_bytes
instead of nr_ptes, nr_pmd, nr_puds.
Apart from reducing number of counters per-mm, the benefit is that we
now calculate oom_badness() more correctly for machines which have
different size of page tables depending on level or where page tables
are less than a page in size.
The only downside can be debuggability because we do not know which page
table level could leak. But I do not remember many bugs that would be
caught by separate counters so I wouldn't lose sleep over this.
[akpm@linux-foundation.org: fix mm/huge_memory.c]
Link: http://lkml.kernel.org/r/20171006100651.44742-2-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
[kirill.shutemov@linux.intel.com: fix build]
Link: http://lkml.kernel.org/r/20171016150113.ikfxy3e7zzfvsr4w@black.fi.intel.com
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Let's add wrappers for ->nr_ptes with the same interface as for nr_pmd
and nr_pud.
The patch also makes nr_ptes accounting dependent onto CONFIG_MMU. Page
table accounting doesn't make sense if you don't have page tables.
It's preparation for consolidation of page-table counters in mm_struct.
Link: http://lkml.kernel.org/r/20171006100651.44742-1-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
On a machine with 5-level paging support a process can allocate
significant amount of memory and stay unnoticed by oom-killer and memory
cgroup. The trick is to allocate a lot of PUD page tables. We don't
account PUD page tables, only PMD and PTE.
We already addressed the same issue for PMD page tables, see commit
dc6c9a35b6 ("mm: account pmd page tables to the process").
Introduction of 5-level paging brings the same issue for PUD page
tables.
The patch expands accounting to PUD level.
[kirill.shutemov@linux.intel.com: s/pmd_t/pud_t/]
Link: http://lkml.kernel.org/r/20171004074305.x35eh5u7ybbt5kar@black.fi.intel.com
[heiko.carstens@de.ibm.com: s390/mm: fix pud table accounting]
Link: http://lkml.kernel.org/r/20171103090551.18231-1-heiko.carstens@de.ibm.com
Link: http://lkml.kernel.org/r/20171002080427.3320-1-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.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>
The kernel may panic when an oom happens without killable process
sometimes it is caused by huge unreclaimable slabs used by kernel.
Although kdump could help debug such problem, however, kdump is not
available on all architectures and it might be malfunction sometime.
And, since kernel already panic it is worthy capturing such information
in dmesg to aid touble shooting.
Print out unreclaimable slab info (used size and total size) which
actual memory usage is not zero (num_objs * size != 0) when
unreclaimable slabs amount is greater than total user memory (LRU
pages).
The output looks like:
Unreclaimable slab info:
Name Used Total
rpc_buffers 31KB 31KB
rpc_tasks 7KB 7KB
ebitmap_node 1964KB 1964KB
avtab_node 5024KB 5024KB
xfs_buf 1402KB 1402KB
xfs_ili 134KB 134KB
xfs_efi_item 115KB 115KB
xfs_efd_item 115KB 115KB
xfs_buf_item 134KB 134KB
xfs_log_item_desc 342KB 342KB
xfs_trans 1412KB 1412KB
xfs_ifork 212KB 212KB
[yang.s@alibaba-inc.com: v11]
Link: http://lkml.kernel.org/r/1507656303-103845-4-git-send-email-yang.s@alibaba-inc.com
Link: http://lkml.kernel.org/r/1507152550-46205-4-git-send-email-yang.s@alibaba-inc.com
Signed-off-by: Yang Shi <yang.s@alibaba-inc.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andrea has noticed that the oom_reaper doesn't invalidate the range via
mmu notifiers (mmu_notifier_invalidate_range_start/end) and that can
corrupt the memory of the kvm guest for example.
tlb_flush_mmu_tlbonly already invokes mmu notifiers but that is not
sufficient as per Andrea:
"mmu_notifier_invalidate_range cannot be used in replacement of
mmu_notifier_invalidate_range_start/end. For KVM
mmu_notifier_invalidate_range is a noop and rightfully so. A MMU
notifier implementation has to implement either ->invalidate_range
method or the invalidate_range_start/end methods, not both. And if you
implement invalidate_range_start/end like KVM is forced to do, calling
mmu_notifier_invalidate_range in common code is a noop for KVM.
For those MMU notifiers that can get away only implementing
->invalidate_range, the ->invalidate_range is implicitly called by
mmu_notifier_invalidate_range_end(). And only those secondary MMUs
that share the same pagetable with the primary MMU (like AMD iommuv2)
can get away only implementing ->invalidate_range"
As the callback is allowed to sleep and the implementation is out of
hand of the MM it is safer to simply bail out if there is an mmu
notifier registered. In order to not fail too early make the
mm_has_notifiers check under the oom_lock and have a little nap before
failing to give the current oom victim some more time to exit.
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20170913113427.2291-1-mhocko@kernel.org
Fixes: aac4536355 ("mm, oom: introduce oom reaper")
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: 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>
This is purely required because exit_aio() may block and exit_mmap() may
never start, if the oom_reap_task cannot start running on a mm with
mm_users == 0.
At the same time if the OOM reaper doesn't wait at all for the memory of
the current OOM candidate to be freed by exit_mmap->unmap_vmas, it would
generate a spurious OOM kill.
If it wasn't because of the exit_aio or similar blocking functions in
the last mmput, it would be enough to change the oom_reap_task() in the
case it finds mm_users == 0, to wait for a timeout or to wait for
__mmput to set MMF_OOM_SKIP itself, but it's not just exit_mmap the
problem here so the concurrency of exit_mmap and oom_reap_task is
apparently warranted.
It's a non standard runtime, exit_mmap() runs without mmap_sem, and
oom_reap_task runs with the mmap_sem for reading as usual (kind of
MADV_DONTNEED).
The race between the two is solved with a combination of
tsk_is_oom_victim() (serialized by task_lock) and MMF_OOM_SKIP
(serialized by a dummy down_write/up_write cycle on the same lines of
the ksm_exit method).
If the oom_reap_task() may be running concurrently during exit_mmap,
exit_mmap will wait it to finish in down_write (before taking down mm
structures that would make the oom_reap_task fail with use after free).
If exit_mmap comes first, oom_reap_task() will skip the mm if
MMF_OOM_SKIP is already set and in turn all memory is already freed and
furthermore the mm data structures may already have been taken down by
free_pgtables.
[aarcange@redhat.com: incremental one liner]
Link: http://lkml.kernel.org/r/20170726164319.GC29716@redhat.com
[rientjes@google.com: remove unused mmput_async]
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1708141733130.50317@chino.kir.corp.google.com
[aarcange@redhat.com: microoptimization]
Link: http://lkml.kernel.org/r/20170817171240.GB5066@redhat.com
Link: http://lkml.kernel.org/r/20170726162912.GA29716@redhat.com
Fixes: 26db62f179 ("oom: keep mm of the killed task available")
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Reported-by: David Rientjes <rientjes@google.com>
Tested-by: David Rientjes <rientjes@google.com>
Reviewed-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Hugh Dickins <hughd@google.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>
For ages we have been relying on TIF_MEMDIE thread flag to mark OOM
victims and then, among other things, to give these threads full access
to memory reserves. There are few shortcomings of this implementation,
though.
First of all and the most serious one is that the full access to memory
reserves is quite dangerous because we leave no safety room for the
system to operate and potentially do last emergency steps to move on.
Secondly this flag is per task_struct while the OOM killer operates on
mm_struct granularity so all processes sharing the given mm are killed.
Giving the full access to all these task_structs could lead to a quick
memory reserves depletion. We have tried to reduce this risk by giving
TIF_MEMDIE only to the main thread and the currently allocating task but
that doesn't really solve this problem while it surely opens up a room
for corner cases - e.g. GFP_NO{FS,IO} requests might loop inside the
allocator without access to memory reserves because a particular thread
was not the group leader.
Now that we have the oom reaper and that all oom victims are reapable
after 1b51e65eab ("oom, oom_reaper: allow to reap mm shared by the
kthreads") we can be more conservative and grant only partial access to
memory reserves because there are reasonable chances of the parallel
memory freeing. We still want some access to reserves because we do not
want other consumers to eat up the victim's freed memory. oom victims
will still contend with __GFP_HIGH users but those shouldn't be so
aggressive to starve oom victims completely.
Introduce ALLOC_OOM flag and give all tsk_is_oom_victim tasks access to
the half of the reserves. This makes the access to reserves independent
on which task has passed through mark_oom_victim. Also drop any usage
of TIF_MEMDIE from the page allocator proper and replace it by
tsk_is_oom_victim as well which will make page_alloc.c completely
TIF_MEMDIE free finally.
CONFIG_MMU=n doesn't have oom reaper so let's stick to the original
ALLOC_NO_WATERMARKS approach.
There is a demand to make the oom killer memcg aware which will imply
many tasks killed at once. This change will allow such a usecase
without worrying about complete memory reserves depletion.
Link: http://lkml.kernel.org/r/20170810075019.28998-2-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
During the debugging of the problem described in
https://lkml.org/lkml/2017/5/17/542 and fixed by Tetsuo Handa in
https://lkml.org/lkml/2017/5/19/383 , I've found that the existing debug
output is not really useful to understand issues related to the oom
reaper.
So, I assume, that adding some tracepoints might help with debugging of
similar issues.
Trace the following events:
1) a process is marked as an oom victim,
2) a process is added to the oom reaper list,
3) the oom reaper starts reaping process's mm,
4) the oom reaper finished reaping,
5) the oom reaper skips reaping.
How it works in practice? Below is an example which show how the problem
mentioned above can be found: one process is added twice to the
oom_reaper list:
$ cd /sys/kernel/debug/tracing
$ echo "oom:mark_victim" > set_event
$ echo "oom:wake_reaper" >> set_event
$ echo "oom:skip_task_reaping" >> set_event
$ echo "oom:start_task_reaping" >> set_event
$ echo "oom:finish_task_reaping" >> set_event
$ cat trace_pipe
allocate-502 [001] .... 91.836405: mark_victim: pid=502
allocate-502 [001] .N.. 91.837356: wake_reaper: pid=502
allocate-502 [000] .N.. 91.871149: wake_reaper: pid=502
oom_reaper-23 [000] .... 91.871177: start_task_reaping: pid=502
oom_reaper-23 [000] .N.. 91.879511: finish_task_reaping: pid=502
oom_reaper-23 [000] .... 91.879580: skip_task_reaping: pid=502
Link: http://lkml.kernel.org/r/20170530185231.GA13412@castle
Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Johannes Weiner <hannes@cmpxchg.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>
Show count of oom killer invocations in /proc/vmstat and count of
processes killed in memory cgroup in knob "memory.events" (in
memory.oom_control for v1 cgroup).
Also describe difference between "oom" and "oom_kill" in memory cgroup
documentation. Currently oom in memory cgroup kills tasks iff shortage
has happened inside page fault.
These counters helps in monitoring oom kills - for now the only way is
grepping for magic words in kernel log.
[akpm@linux-foundation.org: fix for mem_cgroup_count_vm_event() rename]
[akpm@linux-foundation.org: fix comment, per Konstantin]
Link: http://lkml.kernel.org/r/149570810989.203600.9492483715840752937.stgit@buzz
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Roman Guschin <guroan@gmail.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>
Tetsuo has reported that sysrq triggered OOM killer will print a
misleading information when no tasks are selected:
sysrq: SysRq : Manual OOM execution
Out of memory: Kill process 4468 ((agetty)) score 0 or sacrifice child
Killed process 4468 ((agetty)) total-vm:43704kB, anon-rss:1760kB, file-rss:0kB, shmem-rss:0kB
sysrq: SysRq : Manual OOM execution
Out of memory: Kill process 4469 (systemd-cgroups) score 0 or sacrifice child
Killed process 4469 (systemd-cgroups) total-vm:10704kB, anon-rss:120kB, file-rss:0kB, shmem-rss:0kB
sysrq: SysRq : Manual OOM execution
sysrq: OOM request ignored because killer is disabled
sysrq: SysRq : Manual OOM execution
sysrq: OOM request ignored because killer is disabled
sysrq: SysRq : Manual OOM execution
sysrq: OOM request ignored because killer is disabled
The real reason is that there are no eligible tasks for the OOM killer
to select but since commit 7c5f64f844 ("mm: oom: deduplicate victim
selection code for memcg and global oom") the semantic of out_of_memory
has changed without updating moom_callback.
This patch updates moom_callback to tell that no task was eligible which
is the case for both oom killer disabled and no eligible tasks. In
order to help distinguish first case from the second add printk to both
oom_killer_{enable,disable}. This information is useful on its own
because it might help debugging potential memory allocation failures.
Fixes: 7c5f64f844 ("mm: oom: deduplicate victim selection code for memcg and global oom")
Link: http://lkml.kernel.org/r/20170404134705.6361-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We are going to split <linux/sched/task.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/task.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We are going to split <linux/sched/coredump.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/coredump.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We are going to split <linux/sched/mm.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/mm.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
The APIs that are going to be moved first are:
mm_alloc()
__mmdrop()
mmdrop()
mmdrop_async_fn()
mmdrop_async()
mmget_not_zero()
mmput()
mmput_async()
get_task_mm()
mm_access()
mm_release()
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Apart from adding the helper function itself, the rest of the kernel is
converted mechanically using:
git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)->mm_count);/mmgrab\(\1\);/'
git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)\.mm_count);/mmgrab\(\&\1\);/'
This is needed for a later patch that hooks into the helper, but might
be a worthwhile cleanup on its own.
(Michal Hocko provided most of the kerneldoc comment.)
Link: http://lkml.kernel.org/r/20161218123229.22952-1-vegard.nossum@oracle.com
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 82e7d3abec ("oom: print nodemask in the oom report") implicitly
sets the allocation nodemask to cpuset_current_mems_allowed when there
is no effective mempolicy. cpuset_current_mems_allowed is only
effective when cpusets are enabled, which is also printed by
dump_header(), so setting the nodemask to cpuset_current_mems_allowed is
redundant and prevents debugging issues where ac->nodemask is not set
properly in the page allocator.
This provides better debugging output since
cpuset_print_current_mems_allowed() is already provided.
[rientjes@google.com: newline per Hillf]
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1701200158300.88321@chino.kir.corp.google.com
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1701191454470.2381@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Logic on whether we can reap pages from the VMA should match what we
have in madvise_dontneed(). In particular, we should skip, VM_PFNMAP
VMAs, but we don't now.
Let's just extract condition on which we can shoot down pagesi from a
VMA with MADV_DONTNEED into separate function and use it in both places.
Link: http://lkml.kernel.org/r/20170118122429.43661-4-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Peter Zijlstra <peterz@infradead.org>
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>
detail == NULL would give the same functionality as
.check_swap_entries==true.
Link: http://lkml.kernel.org/r/20170118122429.43661-2-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Peter Zijlstra <peterz@infradead.org>
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 only user of ignore_dirty is oom-reaper. But it doesn't really use
it.
ignore_dirty only has effect on file pages mapped with dirty pte. But
oom-repear skips shared VMAs, so there's no way we can dirty file pte in
them.
Link: http://lkml.kernel.org/r/20170118122429.43661-1-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Peter Zijlstra <peterz@infradead.org>
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>
__alloc_pages_may_oom makes sure to skip the OOM killer depending on the
allocation request. This includes lowmem requests, costly high order
requests and others. For a long time __GFP_NOFAIL acted as an override
for all those rules. This is not documented and it can be quite
surprising as well. E.g. GFP_NOFS requests are not invoking the OOM
killer but GFP_NOFS|__GFP_NOFAIL does so if we try to convert some of
the existing open coded loops around allocator to nofail request (and we
have done that in the past) then such a change would have a non trivial
side effect which is far from obvious. Note that the primary motivation
for skipping the OOM killer is to prevent from pre-mature invocation.
The exception has been added by commit 82553a937f ("oom: invoke oom
killer for __GFP_NOFAIL"). The changelog points out that the oom killer
has to be invoked otherwise the request would be looping for ever. But
this argument is rather weak because the OOM killer doesn't really
guarantee a forward progress for those exceptional cases:
- it will hardly help to form costly order which in turn can result in
the system panic because of no oom killable task in the end - I believe
we certainly do not want to put the system down just because there is a
nasty driver asking for order-9 page with GFP_NOFAIL not realizing all
the consequences. It is much better this request would loop for ever
than the massive system disruption
- lowmem is also highly unlikely to be freed during OOM killer
- GFP_NOFS request could trigger while there is still a lot of memory
pinned by filesystems.
This patch simply removes the __GFP_NOFAIL special case in order to have a
more clear semantic without surprising side effects.
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Nils Holland <nholland@tisys.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
show_mem() allows to filter out node specific data which is irrelevant
to the allocation request via SHOW_MEM_FILTER_NODES. The filtering is
done in skip_free_areas_node which skips all nodes which are not in the
mems_allowed of the current process. This works most of the time as
expected because the nodemask shouldn't be outside of the allocating
task but there are some exceptions. E.g. memory hotplug might want to
request allocations from outside of the allowed nodes (see
new_node_page).
Get rid of this hardcoded behavior and push the allocation mask down the
show_mem path and use it instead of cpuset_current_mems_allowed. NULL
nodemask is interpreted as cpuset_current_mems_allowed.
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20170117091543.25850-5-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We have received a hard to explain oom report from a customer. The oom
triggered regardless there is a lot of free memory:
PoolThread invoked oom-killer: gfp_mask=0x280da, order=0, oom_adj=0, oom_score_adj=0
PoolThread cpuset=/ mems_allowed=0-7
Pid: 30055, comm: PoolThread Tainted: G E X 3.0.101-80-default #1
Call Trace:
dump_trace+0x75/0x300
dump_stack+0x69/0x6f
dump_header+0x8e/0x110
oom_kill_process+0xa6/0x350
out_of_memory+0x2b7/0x310
__alloc_pages_slowpath+0x7dd/0x820
__alloc_pages_nodemask+0x1e9/0x200
alloc_pages_vma+0xe1/0x290
do_anonymous_page+0x13e/0x300
do_page_fault+0x1fd/0x4c0
page_fault+0x25/0x30
[...]
active_anon:1135959151 inactive_anon:1051962 isolated_anon:0
active_file:13093 inactive_file:222506 isolated_file:0
unevictable:262144 dirty:2 writeback:0 unstable:0
free:432672819 slab_reclaimable:7917 slab_unreclaimable:95308
mapped:261139 shmem:166297 pagetables:2228282 bounce:0
[...]
Node 0 DMA free:15896kB min:0kB low:0kB high:0kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15672kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes
lowmem_reserve[]: 0 2892 775542 775542
Node 0 DMA32 free:2783784kB min:28kB low:32kB high:40kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:2961572kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes
lowmem_reserve[]: 0 0 772650 772650
Node 0 Normal free:8120kB min:8160kB low:10200kB high:12240kB active_anon:779334960kB inactive_anon:2198744kB active_file:0kB inactive_file:180kB unevictable:131072kB isolated(anon):0kB isolated(file):0kB present:791193600kB mlocked:131072kB dirty:0kB writeback:0kB mapped:372940kB shmem:361480kB slab_reclaimable:4536kB slab_unreclaimable:68472kB kernel_stack:10104kB pagetables:1414820kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:2280 all_unreclaimable? yes
lowmem_reserve[]: 0 0 0 0
Node 1 Normal free:476718144kB min:8192kB low:10240kB high:12288kB active_anon:307623696kB inactive_anon:283620kB active_file:10392kB inactive_file:69908kB unevictable:131072kB isolated(anon):0kB isolated(file):0kB present:794296320kB mlocked:131072kB dirty:4kB writeback:0kB mapped:257208kB shmem:189896kB slab_reclaimable:3868kB slab_unreclaimable:44756kB kernel_stack:1848kB pagetables:1369432kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0 0 0
Node 2 Normal free:386002452kB min:8192kB low:10240kB high:12288kB active_anon:398563752kB inactive_anon:68184kB active_file:10292kB inactive_file:29936kB unevictable:131072kB isolated(anon):0kB isolated(file):0kB present:794296320kB mlocked:131072kB dirty:0kB writeback:0kB mapped:32084kB shmem:776kB slab_reclaimable:6888kB slab_unreclaimable:60056kB kernel_stack:8208kB pagetables:1282880kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0 0 0
Node 3 Normal free:196406760kB min:8192kB low:10240kB high:12288kB active_anon:587445640kB inactive_anon:164396kB active_file:5716kB inactive_file:709844kB unevictable:131072kB isolated(anon):0kB isolated(file):0kB present:794296320kB mlocked:131072kB dirty:0kB writeback:0kB mapped:291776kB shmem:111416kB slab_reclaimable:5152kB slab_unreclaimable:44516kB kernel_stack:2168kB pagetables:1455956kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0 0 0
Node 4 Normal free:425338880kB min:8192kB low:10240kB high:12288kB active_anon:359695204kB inactive_anon:43216kB active_file:5748kB inactive_file:14772kB unevictable:131072kB isolated(anon):0kB isolated(file):0kB present:794296320kB mlocked:131072kB dirty:0kB writeback:0kB mapped:24708kB shmem:1120kB slab_reclaimable:1884kB slab_unreclaimable:41060kB kernel_stack:1856kB pagetables:1100208kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0 0 0
Node 5 Normal free:11140kB min:8192kB low:10240kB high:12288kB active_anon:784240872kB inactive_anon:1217164kB active_file:28kB inactive_file:48kB unevictable:131072kB isolated(anon):0kB isolated(file):0kB present:794296320kB mlocked:131072kB dirty:0kB writeback:0kB mapped:11408kB shmem:0kB slab_reclaimable:2008kB slab_unreclaimable:49220kB kernel_stack:1360kB pagetables:531600kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:1202 all_unreclaimable? yes
lowmem_reserve[]: 0 0 0 0
Node 6 Normal free:243395332kB min:8192kB low:10240kB high:12288kB active_anon:542015544kB inactive_anon:40208kB active_file:968kB inactive_file:8484kB unevictable:131072kB isolated(anon):0kB isolated(file):0kB present:794296320kB mlocked:131072kB dirty:0kB writeback:0kB mapped:19992kB shmem:496kB slab_reclaimable:1672kB slab_unreclaimable:37052kB kernel_stack:2088kB pagetables:750264kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0 0 0
Node 7 Normal free:10768kB min:8192kB low:10240kB high:12288kB active_anon:784916936kB inactive_anon:192316kB active_file:19228kB inactive_file:56852kB unevictable:131072kB isolated(anon):0kB isolated(file):0kB present:794296320kB mlocked:131072kB dirty:4kB writeback:0kB mapped:34440kB shmem:4kB slab_reclaimable:5660kB slab_unreclaimable:36100kB kernel_stack:1328kB pagetables:1007968kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0 0 0
So all nodes but Node 0 have a lot of free memory which should suggest
that there is an available memory especially when mems_allowed=0-7. One
could speculate that a massive process has managed to terminate and free
up a lot of memory while racing with the above allocation request.
Although this is highly unlikely it cannot be ruled out.
A further debugging, however shown that the faulting process had
mempolicy (not cpuset) to bind to Node 0. We cannot see that
information from the report though. mems_allowed turned out to be more
confusing than really helpful.
Fix this by always priting the nodemask. It is either mempolicy mask
(and non-null) or the one defined by the cpusets. The new output for
the above oom report would be
PoolThread invoked oom-killer: gfp_mask=0x280da(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), nodemask=0, order=0, oom_adj=0, oom_score_adj=0
This patch doesn't touch show_mem and the node filtering based on the
cpuset node mask because mempolicy is always a subset of cpusets and
seeing the full cpuset oom context might be helpful for tunning more
specific mempolicies inside cpusets (e.g. when they turn out to be too
restrictive). To prevent from ugly ifdefs the mask is printed even for
!NUMA configurations but this should be OK (a single node will be
printed).
Link: http://lkml.kernel.org/r/20160930214146.28600-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Sellami Abdelkader <abdelkader.sellami@sap.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Sellami Abdelkader <abdelkader.sellami@sap.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit c32b3cbe0d ("oom, PM: make OOM detection in the freezer path
raceless") inserted a WARN_ON() into pagefault_out_of_memory() in order
to warn when we raced with disabling the OOM killer.
Now, patch "oom, suspend: fix oom_killer_disable vs. pm suspend
properly" introduced a timeout for oom_killer_disable(). Even if we
raced with disabling the OOM killer and the system is OOM livelocked,
the OOM killer will be enabled eventually (in 20 seconds by default) and
the OOM livelock will be solved. Therefore, we no longer need to warn
when we raced with disabling the OOM killer.
Link: http://lkml.kernel.org/r/1473442120-7246-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.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>
Since the lumpy reclaim is gone there is no source of higher order pages
if CONFIG_COMPACTION=n except for the order-0 pages reclaim which is
unreliable for that purpose to say the least. Hitting an OOM for
!costly higher order requests is therefore all not that hard to imagine.
We are trying hard to not invoke OOM killer as much as possible but
there is simply no reliable way to detect whether more reclaim retries
make sense.
Disabling COMPACTION is not widespread but it seems that some users
might have disable the feature without realizing full consequences
(mostly along with disabling THP because compaction used to be THP
mainly thing). This patch just adds a note if the OOM killer was
triggered by higher order request with compaction disabled. This will
help us identifying possible misconfiguration right from the oom report
which is easier than to always keep in mind that somebody might have
disabled COMPACTION without a good reason.
Link: http://lkml.kernel.org/r/20160830111632.GD23963@dhcp22.suse.cz
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
oom reaper was skipped for an mm which is shared with the kernel thread
(aka use_mm()). The primary concern was that such a kthread might want
to read from the userspace memory and see zero page as a result of the
oom reaper action. This is no longer a problem after "mm: make sure
that kthreads will not refault oom reaped memory" because any attempt to
fault in when the MMF_UNSTABLE is set will result in SIGBUS and so the
target user should see an error. This means that we can finally allow
oom reaper also to tasks which share their mm with kthreads.
Link: http://lkml.kernel.org/r/1472119394-11342-10-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.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>
There are only few use_mm() users in the kernel right now. Most of them
write to the target memory but vhost driver relies on
copy_from_user/get_user from a kernel thread context. This makes it
impossible to reap the memory of an oom victim which shares the mm with
the vhost kernel thread because it could see a zero page unexpectedly
and theoretically make an incorrect decision visible outside of the
killed task context.
To quote Michael S. Tsirkin:
: Getting an error from __get_user and friends is handled gracefully.
: Getting zero instead of a real value will cause userspace
: memory corruption.
The vhost kernel thread is bound to an open fd of the vhost device which
is not tight to the mm owner life cycle in general. The device fd can
be inherited or passed over to another process which means that we
really have to be careful about unexpected memory corruption because
unlike for normal oom victims the result will be visible outside of the
oom victim context.
Make sure that no kthread context (users of use_mm) can ever see
corrupted data because of the oom reaper and hook into the page fault
path by checking MMF_UNSTABLE mm flag. __oom_reap_task_mm will set the
flag before it starts unmapping the address space while the flag is
checked after the page fault has been handled. If the flag is set then
SIGBUS is triggered so any g-u-p user will get a error code.
Regular tasks do not need this protection because all which share the mm
are killed when the mm is reaped and so the corruption will not outlive
them.
This patch shouldn't have any visible effect at this moment because the
OOM killer doesn't invoke oom reaper for tasks with mm shared with
kthreads yet.
Link: http://lkml.kernel.org/r/1472119394-11342-9-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.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>
There are no users of exit_oom_victim on !current task anymore so enforce
the API to always work on the current.
Link: http://lkml.kernel.org/r/1472119394-11342-8-git-send-email-mhocko@kernel.org
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.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>
Commit 7407054209 ("oom, suspend: fix oom_reaper vs.
oom_killer_disable race") has workaround an existing race between
oom_killer_disable and oom_reaper by adding another round of
try_to_freeze_tasks after the oom killer was disabled. This was the
easiest thing to do for a late 4.7 fix. Let's fix it properly now.
After "oom: keep mm of the killed task available" we no longer have to
call exit_oom_victim from the oom reaper because we have stable mm
available and hide the oom_reaped mm by MMF_OOM_SKIP flag. So let's
remove exit_oom_victim and the race described in the above commit
doesn't exist anymore if.
Unfortunately this alone is not sufficient for the oom_killer_disable
usecase because now we do not have any reliable way to reach
exit_oom_victim (the victim might get stuck on a way to exit for an
unbounded amount of time). OOM killer can cope with that by checking mm
flags and move on to another victim but we cannot do the same for
oom_killer_disable as we would lose the guarantee of no further
interference of the victim with the rest of the system. What we can do
instead is to cap the maximum time the oom_killer_disable waits for
victims. The only current user of this function (pm suspend) already
has a concept of timeout for back off so we can reuse the same value
there.
Let's drop set_freezable for the oom_reaper kthread because it is no
longer needed as the reaper doesn't wake or thaw any processes.
Link: http://lkml.kernel.org/r/1472119394-11342-7-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.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>
After "oom: keep mm of the killed task available" we can safely detect
an oom victim by checking task->signal->oom_mm so we do not need the
signal_struct counter anymore so let's get rid of it.
This alone wouldn't be sufficient for nommu archs because
exit_oom_victim doesn't hide the process from the oom killer anymore.
We can, however, mark the mm with a MMF flag in __mmput. We can reuse
MMF_OOM_REAPED and rename it to a more generic MMF_OOM_SKIP.
Link: http://lkml.kernel.org/r/1472119394-11342-6-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.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>
oom_reap_task has to call exit_oom_victim in order to make sure that the
oom vicim will not block the oom killer for ever. This is, however,
opening new problems (e.g oom_killer_disable exclusion - see commit
7407054209 ("oom, suspend: fix oom_reaper vs. oom_killer_disable
race")). exit_oom_victim should be only called from the victim's
context ideally.
One way to achieve this would be to rely on per mm_struct flags. We
already have MMF_OOM_REAPED to hide a task from the oom killer since
"mm, oom: hide mm which is shared with kthread or global init". The
problem is that the exit path:
do_exit
exit_mm
tsk->mm = NULL;
mmput
__mmput
exit_oom_victim
doesn't guarantee that exit_oom_victim will get called in a bounded
amount of time. At least exit_aio depends on IO which might get blocked
due to lack of memory and who knows what else is lurking there.
This patch takes a different approach. We remember tsk->mm into the
signal_struct and bind it to the signal struct life time for all oom
victims. __oom_reap_task_mm as well as oom_scan_process_thread do not
have to rely on find_lock_task_mm anymore and they will have a reliable
reference to the mm struct. As a result all the oom specific
communication inside the OOM killer can be done via tsk->signal->oom_mm.
Increasing the signal_struct for something as unlikely as the oom killer
is far from ideal but this approach will make the code much more
reasonable and long term we even might want to move task->mm into the
signal_struct anyway. In the next step we might want to make the oom
killer exclusion and access to memory reserves completely independent
which would be also nice.
Link: http://lkml.kernel.org/r/1472119394-11342-4-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.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>
"mm, oom_reaper: do not attempt to reap a task twice" tried to give the
OOM reaper one more chance to retry using MMF_OOM_NOT_REAPABLE flag.
But the usefulness of the flag is rather limited and actually never
shown in practice. If the flag is set, it means that the holder of
mm->mmap_sem cannot call up_write() due to presumably being blocked at
unkillable wait waiting for other thread's memory allocation. But since
one of threads sharing that mm will queue that mm immediately via
task_will_free_mem() shortcut (otherwise, oom_badness() will select the
same mm again due to oom_score_adj value unchanged), retrying
MMF_OOM_NOT_REAPABLE mm is unlikely helpful.
Let's always set MMF_OOM_REAPED.
Link: http://lkml.kernel.org/r/1472119394-11342-3-git-send-email-mhocko@kernel.org
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.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>
Patch series "fortify oom killer even more", v2.
This patch (of 9):
__oom_reap_task() can be simplified a bit if it receives a valid mm from
oom_reap_task() which also uses that mm when __oom_reap_task() failed.
We can drop one find_lock_task_mm() call and also make the
__oom_reap_task() code flow easier to follow. Moreover, this will make
later patch in the series easier to review. Pinning mm's mm_count for
longer time is not really harmful because this will not pin much memory.
This patch doesn't introduce any functional change.
Link: http://lkml.kernel.org/r/1472119394-11342-2-git-send-email-mhocko@kernel.org
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.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>
When selecting an oom victim, we use the same heuristic for both memory
cgroup and global oom. The only difference is the scope of tasks to
select the victim from. So we could just export an iterator over all
memcg tasks and keep all oom related logic in oom_kill.c, but instead we
duplicate pieces of it in memcontrol.c reusing some initially private
functions of oom_kill.c in order to not duplicate all of it. That looks
ugly and error prone, because any modification of select_bad_process
should also be propagated to mem_cgroup_out_of_memory.
Let's rework this as follows: keep all oom heuristic related code private
to oom_kill.c and make oom_kill.c use exported memcg functions when it's
really necessary (like in case of iterating over memcg tasks).
Link: http://lkml.kernel.org/r/1470056933-7505-1-git-send-email-vdavydov@virtuozzo.com
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Michal Hocko