Messages in this thread | | | Date | Mon, 10 Sep 2018 17:40:20 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [PATCH RFC] mm: don't raise MEMCG_OOM event due to failed high-order allocation |
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On Mon, 10 Sep 2018, Roman Gushchin wrote:
> The memcg OOM killer is never invoked due to a failed high-order > allocation, however the MEMCG_OOM event can be easily raised. > > Under some memory pressure it can happen easily because of a > concurrent allocation. Let's look at try_charge(). Even if we were > able to reclaim enough memory, this check can fail due to a race > with another allocation: > > if (mem_cgroup_margin(mem_over_limit) >= nr_pages) > goto retry; > > For regular pages the following condition will save us from triggering > the OOM: > > if (nr_reclaimed && nr_pages <= (1 << PAGE_ALLOC_COSTLY_ORDER)) > goto retry; > > But for high-order allocation this condition will intentionally fail. > The reason behind is that we'll likely fall to regular pages anyway, > so it's ok and even preferred to return ENOMEM. > > In this case the idea of raising the MEMCG_OOM event looks dubious. > > Fix this by moving MEMCG_OOM raising to mem_cgroup_oom() after > allocation order check, so that the event won't be raised for high > order allocations. > > Signed-off-by: Roman Gushchin <guro@fb.com> > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
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