Re: [PATCH] mm,oom: fix oom invocation issues

[Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>]

Roman Gushchin wrote:
> On Wed, May 17, 2017 at 06:14:46PM +0200, Michal Hocko wrote:
> > On Wed 17-05-17 16:26:20, Roman Gushchin wrote:
> > [...]
> > > [   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
> > 
> > Are there any oom_reaper messages? Could you provide the full kernel log
> > please?
> 
> Sure. Sorry, it was too bulky, so I've cut the line about oom_reaper by mistake.
> Here it is:
> --------------------------------------------------------------------------------
> [   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

> [   25.759892] Node 0 DMA32 free:44700kB min:44704kB low:55880kB high:67056kB active_anon:1944216kB inactive_anon:204kB active_file:592kB inactive_file:0kB unevictable:0kB writepending:304kB present:2080640kB managed:2031972kB mlocked:0kB slab_reclaimable:11336kB slab_unreclaimable:9784kB kernel_stack:1776kB pagetables:6932kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB

> [   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

This is a side effect of commit 9a67f6488eca926f ("mm: consolidate GFP_NOFAIL
checks in the allocator slowpath") which I noticed at
http://lkml.kernel.org/r/e7f932bf-313a-917d-6304-81528aca5994@I-love.SAKURA.ne.jp .

> [   25.804499] Node 0 DMA32 free:251876kB min:44704kB low:55880kB high:67056kB active_anon:1737368kB inactive_anon:204kB active_file:592kB inactive_file:0kB unevictable:0kB writepending:304kB present:2080640kB managed:2031972kB mlocked:0kB slab_reclaimable:10312kB slab_unreclaimable:9784kB kernel_stack:1776kB pagetables:6932kB bounce:0kB free_pcp:700kB local_pcp:0kB free_cma:0kB

> [   25.817589] allocate invoked oom-killer: gfp_mask=0x0(), nodemask=(null),  order=0, oom_score_adj=0
> [   25.818821] allocate cpuset=/ mems_allowed=0

Since pagefault_out_of_memory() is unconditionally called if a normal allocation failed,
that commit made pagefault_out_of_memory() to be called if current thread was selected as
an OOM victim, despite the system is no longer under memory pressure because the OOM reaper
has reclaimed memory.

> [   25.835784] Node 0 DMA32 free:1934360kB min:44704kB low:55880kB high:67056kB active_anon:57104kB inactive_anon:204kB active_file:416kB inactive_file:2476kB unevictable:0kB writepending:424kB present:2080640kB managed:2031972kB mlocked:0kB slab_reclaimable:10236kB slab_unreclaimable:9584kB kernel_stack:1776kB pagetables:3604kB bounce:0kB free_pcp:144kB local_pcp:0kB free_cma:0kB

> [   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
> --------------------------------------------------------------------------------

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