The patch titled Subject: mm/page_alloc.c: make sure OOM victim can try allocations with no watermarks once has been added to the -mm tree. Its filename is mmpage_alloc-make-sure-oom-victim-can-try-allocations-with-no-watermarks-once.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mmpage_alloc-make-sure-oom-victim-can-try-allocations-with-no-watermarks-once.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mmpage_alloc-make-sure-oom-victim-can-try-allocations-with-no-watermarks-once.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Subject: mm/page_alloc.c: make sure OOM victim can try allocations with no watermarks once Roman Gushchin has reported that the OOM killer can trivially selects next OOM victim when a thread doing memory allocation from page fault path was selected as first OOM victim. ---------- [ 25.721494] allocate invoked oom-killer: gfp_mask=0x14280ca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), nodemask=(null), order=0, oom_score_adj=0 [ 25.725658] allocate cpuset=/ mems_allowed=0 [ 25.727033] CPU: 1 PID: 492 Comm: allocate Not tainted 4.12.0-rc1-mm1+ #181 [ 25.729215] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 [ 25.729598] Call Trace: [ 25.729598] dump_stack+0x63/0x82 [ 25.729598] dump_header+0x97/0x21a [ 25.729598] ? do_try_to_free_pages+0x2d7/0x360 [ 25.729598] ? security_capable_noaudit+0x45/0x60 [ 25.729598] oom_kill_process+0x219/0x3e0 [ 25.729598] out_of_memory+0x11d/0x480 [ 25.729598] __alloc_pages_slowpath+0xc84/0xd40 [ 25.729598] __alloc_pages_nodemask+0x245/0x260 [ 25.729598] alloc_pages_vma+0xa2/0x270 [ 25.729598] __handle_mm_fault+0xca9/0x10c0 [ 25.729598] handle_mm_fault+0xf3/0x210 [ 25.729598] __do_page_fault+0x240/0x4e0 [ 25.729598] trace_do_page_fault+0x37/0xe0 [ 25.729598] do_async_page_fault+0x19/0x70 [ 25.729598] async_page_fault+0x28/0x30 (...snipped...) [ 25.781882] Out of memory: Kill process 492 (allocate) score 899 or sacrifice child [ 25.783874] Killed process 492 (allocate) total-vm:2052368kB, anon-rss:1894576kB, file-rss:4kB, shmem-rss:0kB [ 25.785680] allocate: page allocation failure: order:0, mode:0x14280ca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), nodemask=(null) [ 25.786797] allocate cpuset=/ mems_allowed=0 [ 25.787246] CPU: 1 PID: 492 Comm: allocate Not tainted 4.12.0-rc1-mm1+ #181 [ 25.787935] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 [ 25.788867] Call Trace: [ 25.789119] dump_stack+0x63/0x82 [ 25.789451] warn_alloc+0x114/0x1b0 [ 25.789451] __alloc_pages_slowpath+0xd32/0xd40 [ 25.789451] __alloc_pages_nodemask+0x245/0x260 [ 25.789451] alloc_pages_vma+0xa2/0x270 [ 25.789451] __handle_mm_fault+0xca9/0x10c0 [ 25.789451] handle_mm_fault+0xf3/0x210 [ 25.789451] __do_page_fault+0x240/0x4e0 [ 25.789451] trace_do_page_fault+0x37/0xe0 [ 25.789451] do_async_page_fault+0x19/0x70 [ 25.789451] async_page_fault+0x28/0x30 (...snipped...) [ 25.810868] oom_reaper: reaped process 492 (allocate), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB (...snipped...) [ 25.817589] allocate invoked oom-killer: gfp_mask=0x0(), nodemask=(null), order=0, oom_score_adj=0 [ 25.818821] allocate cpuset=/ mems_allowed=0 [ 25.819259] CPU: 1 PID: 492 Comm: allocate Not tainted 4.12.0-rc1-mm1+ #181 [ 25.819847] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 [ 25.820549] Call Trace: [ 25.820733] dump_stack+0x63/0x82 [ 25.820961] dump_header+0x97/0x21a [ 25.820961] ? security_capable_noaudit+0x45/0x60 [ 25.820961] oom_kill_process+0x219/0x3e0 [ 25.820961] out_of_memory+0x11d/0x480 [ 25.820961] pagefault_out_of_memory+0x68/0x80 [ 25.820961] mm_fault_error+0x8f/0x190 [ 25.820961] ? handle_mm_fault+0xf3/0x210 [ 25.820961] __do_page_fault+0x4b2/0x4e0 [ 25.820961] trace_do_page_fault+0x37/0xe0 [ 25.820961] do_async_page_fault+0x19/0x70 [ 25.820961] async_page_fault+0x28/0x30 (...snipped...) [ 25.863078] Out of memory: Kill process 233 (firewalld) score 10 or sacrifice child [ 25.863634] Killed process 233 (firewalld) total-vm:246076kB, anon-rss:20956kB, file-rss:0kB, shmem-rss:0kB ---------- There is a race window that the OOM reaper completes reclaiming the first victim's memory while nothing but mutex_trylock() prevents the first victim from calling out_of_memory() from pagefault_out_of_memory() after memory allocation for page fault path failed due to being selected as an OOM victim. This is a side effect of commit 9a67f6488eca926f ("mm: consolidate GFP_NOFAIL checks in the allocator slowpath") because that commit silently changed the behavior from /* Avoid allocations with no watermarks from looping endlessly */ to /* * Give up allocations without trying memory reserves if selected * as an OOM victim */ in __alloc_pages_slowpath() by moving the location to check TIF_MEMDIE flag. I have noticed this change but I didn't post a patch because I thought it is an acceptable change other than noise by warn_alloc() because !__GFP_NOFAIL allocations are allowed to fail. But we overlooked that failing memory allocation from page fault path makes difference due to the race window explained above. While it might be possible to add a check to pagefault_out_of_memory() that prevents the first victim from calling out_of_memory() or remove out_of_memory() from pagefault_out_of_memory(), changing pagefault_out_of_memory() does not suppress noise by warn_alloc() when allocating thread was selected as an OOM victim. There is little point with printing similar backtraces and memory information from both out_of_memory() and warn_alloc(). Instead, if we guarantee that current thread can try allocations with no watermarks once when current thread looping inside __alloc_pages_slowpath() was selected as an OOM victim, we can follow "who can use memory reserves" rules and suppress noise by warn_alloc() and prevent memory allocations from page fault path from calling pagefault_out_of_memory(). If we take the comment literally, this patch would do : - if (test_thread_flag(TIF_MEMDIE)) : - goto nopage; : + if (alloc_flags == ALLOC_NO_WATERMARKS || (gfp_mask & __GFP_NOMEMALLOC)) : + goto nopage; because gfp_pfmemalloc_allowed() returns false if __GFP_NOMEMALLOC is given. But if I recall correctly (I couldn't find the message), the condition is meant to apply to only OOM victims despite the comment. Therefore, this patch preserves TIF_MEMDIE check. Fixes: 9a67f6488eca926f ("mm: consolidate GFP_NOFAIL checks in the allocator slowpath") Link: http://lkml.kernel.org/r/201705192112.IAF69238.OQOHSJLFOFFMtV@xxxxxxxxxxxxxxxxxxx Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Reported-by: Roman Gushchin <guro@xxxxxx> Tested-by: Roman Gushchin <guro@xxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [4.11] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff -puN mm/page_alloc.c~mmpage_alloc-make-sure-oom-victim-can-try-allocations-with-no-watermarks-once mm/page_alloc.c --- a/mm/page_alloc.c~mmpage_alloc-make-sure-oom-victim-can-try-allocations-with-no-watermarks-once +++ a/mm/page_alloc.c @@ -3870,7 +3870,9 @@ retry: goto got_pg; /* Avoid allocations with no watermarks from looping endlessly */ - if (test_thread_flag(TIF_MEMDIE)) + if (test_thread_flag(TIF_MEMDIE) && + (alloc_flags == ALLOC_NO_WATERMARKS || + (gfp_mask & __GFP_NOMEMALLOC))) goto nopage; /* Retry as long as the OOM killer is making progress */ _ Patches currently in -mm which might be from penguin-kernel@xxxxxxxxxxxxxxxxxxx are mmpage_alloc-make-sure-oom-victim-can-try-allocations-with-no-watermarks-once.patch