linux-kernel - Re: [RFC 0/1] add support for reclaiming priorities per mem cgroup

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Message-ID: <CAEe=Sxmj6wHN9HzAix9F4HDhk9ojYaMrStE1b1MxB0VvMzd=Ug@mail.gmail.com>
Date:   Thu, 30 Mar 2017 14:54:28 -0700
From:   Tim Murray <timmurray@...gle.com>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, cgroups@...r.kernel.org,
        Linux-MM <linux-mm@...ck.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Patrik Torstensson <totte@...gle.com>,
        Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [RFC 0/1] add support for reclaiming priorities per mem cgroup

On Thu, Mar 30, 2017 at 12:40 PM, Tim Murray <timmurray@...gle.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.