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References: <20170317231636.142311-1-timmurray@google.com> <20170330155123.GA3929@cmpxchg.org>
 <CAEe=SxmpXD=f9N_i+xe6gFUKKUefJYvBd8dSwxSM+7rbBBTniw@mail.gmail.com>
From: Tim Murray <timmurray@google.com>
Date: Thu, 30 Mar 2017 14:54:28 -0700
Message-ID: <CAEe=Sxmj6wHN9HzAix9F4HDhk9ojYaMrStE1b1MxB0VvMzd=Ug@mail.gmail.com>
Subject: Re: [RFC 0/1] add support for reclaiming priorities per mem cgroup
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To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>, Vladimir Davydov <vdavydov.dev@gmail.com>, LKML <linux-kernel@vger.kernel.org>, cgroups@vger.kernel.org, Linux-MM <linux-mm@kvack.org>, Suren Baghdasaryan <surenb@google.com>, Patrik Torstensson <totte@google.com>, Android Kernel Team <kernel-team@android.com>

On Thu, Mar 30, 2017 at 12:40 PM, Tim Murray <timmurray@google.com> wrote:
> The current critical vmpressure event
> hasn't been that successful in avoiding oom-killer (on 3.18, at
> least)--I've been able to get oom-killer to trigger without a
> vmpressure event.

Looked at this some more, and this is almost certainly because
vmpressure relies on workqueues. Scheduling delay from CFS workqueues
would explain vmpressure latency that results in oom-killer running
long before the critical vmpressure notification is received in
userspace, even if userspace is running as FIFO. We regularly see
10ms+ latency on workqueues, even when an Android device isn't heavily
loaded.

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