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

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Message-ID: <20190311223631.GA872@sultan-box.localdomain>
Date:   Mon, 11 Mar 2019 15:36:31 -0700
From:   Sultan Alsawaf <sultan@...neltoast.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     Michal Hocko <mhocko@...nel.org>,
        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 Mon, Mar 11, 2019 at 03:15:35PM -0700, Suren Baghdasaryan wrote:
> This what LMKD currently is - a userspace RT process.
> My point was that this page allocation queue that you implemented
> can't be implemented in userspace, at least not without extensive
> communication with kernel.

Oh, that's easy to address. My page allocation queue and the decision on when to
kill a process are orthogonal. In fact, the page allocation queue could be
touched up a bit to factor in the issues Michal mentioned, and it can be
implemented as an improvement to the existing OOM killer. The point of it is
just to ensure that page allocation requests that have gone OOM are given
priority over other allocation requests when free pages start to trickle in.

Userspace doesn't need to know about the page allocation queue, and the queue is
not necessary to implement the method of determining when to kill processes that
I've proposed. It's an optimization, not a necessity.

Thanks,
Sultan