If the OOM killer is invoked when many threads are looping inside the
page allocator, it is possible that the OOM killer is preempted by other
threads. As a result, the OOM killer is unable to send SIGKILL to OOM
victims and/or wake up the OOM reaper by releasing oom_lock for minutes
because other threads consume a lot of CPU time for pointless direct
reclaim.
----------
[ 2802.635229] Killed process 7267 (a.out) total-vm:4176kB, anon-rss:84kB, file-rss:0kB, shmem-rss:0kB
[ 2802.644296] oom_reaper: reaped process 7267 (a.out), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
[ 2802.650237] Out of memory: Kill process 7268 (a.out) score 999 or sacrifice child
[ 2803.653052] Killed process 7268 (a.out) total-vm:4176kB, anon-rss:84kB, file-rss:0kB, shmem-rss:0kB
[ 2804.426183] oom_reaper: reaped process 7268 (a.out), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
[ 2804.432524] Out of memory: Kill process 7269 (a.out) score 999 or sacrifice child
[ 2805.349380] a.out: page allocation stalls for 10047ms, order:0, mode:0x24280ca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO)
[ 2805.349383] CPU: 2 PID: 7243 Comm: a.out Not tainted 4.9.0-rc8 #62
(...snipped...)
[ 3540.977499] a.out 7269 22716.893359 5272 120
[ 3540.977499] 0.000000 1447.601063 0.000000
[ 3540.977499] 0 0
[ 3540.977500] /autogroup-155
----------
This patch adds extra sleeps which is effectively equivalent to
if (mutex_lock_killable(&oom_lock) == 0)
mutex_unlock(&oom_lock);
before retrying allocation at __alloc_pages_may_oom() so that the
OOM killer is not preempted by other threads waiting for the OOM
killer/reaper to reclaim memory. Since the OOM reaper grabs oom_lock
due to commit e2fe14564d3316d1 ("oom_reaper: close race with exiting
task"), waking up other threads before the OOM reaper is woken up by
directly waiting for oom_lock might not help so much.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 51cbe1e..e5c1102 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3060,6 +3060,7 @@ void warn_alloc(gfp_t gfp_mask, const char *fmt, ...)
.order = order,
};
struct page *page;
+ static bool wait_more;
*did_some_progress = 0;
@@ -3070,6 +3071,9 @@ void warn_alloc(gfp_t gfp_mask, const char *fmt, ...)
if (!mutex_trylock(&oom_lock)) {
*did_some_progress = 1;
schedule_timeout_uninterruptible(1);
+ while (wait_more)
+ if (schedule_timeout_killable(1) < 0)
+ break;
return NULL;
}
@@ -3109,6 +3113,7 @@ void warn_alloc(gfp_t gfp_mask, const char *fmt, ...)
if (gfp_mask & __GFP_THISNODE)
goto out;
}
+ wait_more = true;
/* Exhausted what can be done so it's blamo time */
if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) {
*did_some_progress = 1;
@@ -3125,6 +3130,7 @@ void warn_alloc(gfp_t gfp_mask, const char *fmt, ...)
ALLOC_NO_WATERMARKS, ac);
}
}
+ wait_more = false;
out:
mutex_unlock(&oom_lock);
return page;
--
1.8.3.1
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