Michal Hocko wrote:
> On Thu 07-12-17 20:42:20, Tetsuo Handa wrote:
> > Manish Jaggi noticed that running LTP oom01/oom02 ltp tests with high core
> > count causes random kernel panics when an OOM victim which consumed memory
> > in a way the OOM reaper does not help was selected by the OOM killer [1].
> > Since commit 696453e66630ad45 ("mm, oom: task_will_free_mem should skip
> > oom_reaped tasks") changed task_will_free_mem(current) in out_of_memory()
> > to return false as soon as MMF_OOM_SKIP is set, many threads sharing the
> > victim's mm were not able to try allocation from memory reserves after the
> > OOM reaper gave up reclaiming memory.
> >
> > Therefore, this patch allows OOM victims to use ALLOC_OOM watermark for
> > last second allocation attempt.
> >
> > [1] http://lkml.kernel.org/r/e6c83a26-1d59-4afd-55cf-04e58bdde188@xxxxxxxxxxxxxxxxxx
> >
> > Fixes: 696453e66630ad45 ("mm, oom: task_will_free_mem should skip oom_reaped tasks")
> > Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> > Reported-by: Manish Jaggi <mjaggi@xxxxxxxxxxxxxxxxxx>
> > Acked-by: Michal Hocko <mhocko@xxxxxxxx>
>
> I haven't acked _this_ patch! I will have a look but the patch is
> different enough from the original that keeping any acks or reviews is
> inappropriate. Do not do it again!
I see. But nothing has changed except that this is called before entering
into the OOM killer. I assumed that this is a trivial change.
>
> > Cc: Michal Hocko <mhocko@xxxxxxxx>
> > Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
> > Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
> > Cc: David Rientjes <rientjes@xxxxxxxxxx>
> > Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> > ---
> > mm/page_alloc.c | 39 +++++++++++++++++++++++++++++----------
> > 1 file changed, 29 insertions(+), 10 deletions(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 73f5d45..5d054a4 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -3309,6 +3309,10 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
> > return page;
> > }
> >
> > +static struct page *alloc_pages_before_oomkill(gfp_t gfp_mask,
> > + unsigned int order,
> > + const struct alloc_context *ac);
> > +
> > static inline struct page *
> > __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
> > const struct alloc_context *ac, unsigned long *did_some_progress)
> > @@ -3334,16 +3338,7 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
> > return NULL;
> > }
> >
> > - /*
> > - * Go through the zonelist yet one more time, keep very high watermark
> > - * here, this is only to catch a parallel oom killing, we must fail if
> > - * we're still under heavy pressure. But make sure that this reclaim
> > - * attempt shall not depend on __GFP_DIRECT_RECLAIM && !__GFP_NORETRY
> > - * allocation which will never fail due to oom_lock already held.
> > - */
> > - page = get_page_from_freelist((gfp_mask | __GFP_HARDWALL) &
> > - ~__GFP_DIRECT_RECLAIM, order,
> > - ALLOC_WMARK_HIGH|ALLOC_CPUSET, ac);
> > + page = alloc_pages_before_oomkill(gfp_mask, order, ac);
> > if (page)
> > goto out;
> >
> > @@ -3755,6 +3750,30 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
> > return !!__gfp_pfmemalloc_flags(gfp_mask);
> > }
> >
> > +static struct page *alloc_pages_before_oomkill(gfp_t gfp_mask,
> > + unsigned int order,
> > + const struct alloc_context *ac)
> > +{
> > + /*
> > + * Go through the zonelist yet one more time, keep very high watermark
> > + * here, this is only to catch a parallel oom killing, we must fail if
> > + * we're still under heavy pressure. But make sure that this reclaim
> > + * attempt shall not depend on __GFP_DIRECT_RECLAIM && !__GFP_NORETRY
> > + * allocation which will never fail due to oom_lock already held.
> > + * Also, make sure that OOM victims can try ALLOC_OOM watermark
> > + * in case they haven't tried ALLOC_OOM watermark.
> > + */
> > + int alloc_flags = ALLOC_CPUSET | ALLOC_WMARK_HIGH;
> > + int reserve_flags;
> > +
> > + gfp_mask |= __GFP_HARDWALL;
> > + gfp_mask &= ~__GFP_DIRECT_RECLAIM;
> > + reserve_flags = __gfp_pfmemalloc_flags(gfp_mask);
> > + if (reserve_flags)
> > + alloc_flags = reserve_flags;
> > + return get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
> > +}
> > +
> > /*
> > * Checks whether it makes sense to retry the reclaim to make a forward progress
> > * for the given allocation request.
> > --
> > 1.8.3.1
> >
>
> --
> Michal Hocko
> SUSE Labs
>
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