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

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Date:   Tue, 7 May 2019 00:27:21 -0700
From:   Sultan Alsawaf <sultan@...neltoast.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "open list:ANDROID DRIVERS" <devel@...verdev.osuosl.org>,
        Daniel Colascione <dancol@...gle.com>,
        kernel-team <kernel-team@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Tim Murray <timmurray@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        linux-mm <linux-mm@...ck.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Ingo Molnar <mingo@...hat.com>,
        Martijn Coenen <maco@...roid.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Andy Lutomirski <luto@...capital.net>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Christian Brauner <christian@...uner.io>
Subject: Re: [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android

On Tue, May 07, 2019 at 09:04:30AM +0200, Greg Kroah-Hartman wrote:
> Um, why can't "all" Android devices take the same patches that the Pixel
> phones are using today?  They should all be in the public android-common
> kernel repositories that all Android devices should be syncing with on a
> weekly/monthly basis anyway, right?
> 
> thanks,
> 
> greg k-h

Hi Greg,

I only see PSI present in the android-common kernels for 4.9 and above. The vast
majority of Android devices do not run a 4.9+ kernel. It seems unreasonable to
expect OEMs to toil with backporting PSI themselves to get decent memory
management.

But even if they did backport PSI, it wouldn't help too much because a
PSI-enabled LMKD solution is not ready yet. It looks like a PSI-based LMKD is
still under heavy development and won't be ready for all Android devices for
quite some time.

Additionally, it looks like the supposedly-dead lowmemorykiller.c is still being
actively tweaked by Google [1], which does not instill confidence that a
definitive LMK solution a la PSI is coming any time soon.

Thanks,
Sultan

[1] https://android.googlesource.com/kernel/common/+/152bacdd85c46f0c76b00c4acc253e414513634c