linux-kernel - Re: [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android

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Message-ID: <20190312152541.GI19508@bombadil.infradead.org>
Date:   Tue, 12 Mar 2019 08:25:41 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Suren Baghdasaryan <surenb@...gle.com>,
        Sultan Alsawaf <sultan@...neltoast.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Christian Brauner <christian@...uner.io>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>, devel@...verdev.osuosl.org,
        linux-mm <linux-mm@...ck.org>, Tim Murray <timmurray@...gle.com>
Subject: Re: [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android

On Tue, Mar 12, 2019 at 09:05:32AM +0100, Michal Hocko wrote:
> On Mon 11-03-19 15:15:35, Suren Baghdasaryan wrote:
> > Yeah, killing speed is a well-known problem which we are considering
> > in LMKD. For example the recent LMKD change to assign process being
> > killed to a cpuset cgroup containing big cores cuts the kill time
> > considerably. This is not ideal and we are thinking about better ways
> > to expedite the cleanup process.
> 
> If you design is relies on the speed of killing then it is fundamentally
> flawed AFAICT. You cannot assume anything about how quickly a task dies.
> It might be blocked in an uninterruptible sleep or performin an
> operation which takes some time. Sure, oom_reaper might help here but
> still.

Many UNINTERRUPTIBLE sleeps can be converted to KILLABLE sleeps.  It just
needs someone to do the work.