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

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Message-ID: <20190507070430.GA24150@kroah.com>
Date:   Tue, 7 May 2019 09:04:30 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Sultan Alsawaf <sultan@...neltoast.com>
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 Mon, May 06, 2019 at 07:16:22PM -0700, Sultan Alsawaf wrote:
> This is a complete low memory killer solution for Android that is small
> and simple. Processes are killed according to the priorities that
> Android gives them, so that the least important processes are always
> killed first. Processes are killed until memory deficits are satisfied,
> as observed from kswapd struggling to free up pages. Simple LMK stops
> killing processes when kswapd finally goes back to sleep.
> 
> The only tunables are the desired amount of memory to be freed per
> reclaim event and desired frequency of reclaim events. Simple LMK tries
> to free at least the desired amount of memory per reclaim and waits
> until all of its victims' memory is freed before proceeding to kill more
> processes.
> 
> Signed-off-by: Sultan Alsawaf <sultan@...neltoast.com>
> ---
> Hello everyone,
> 
> I've addressed some of the concerns that were brought up with the first version
> of the Simple LMK patch. I understand that a kernel-based solution like this
> that contains policy decisions for a specific userspace is not the way to go,
> but the Android ecosystem still has a pressing need for a low memory killer that
> works well.
> 
> Most Android devices still use the ancient and deprecated lowmemorykiller.c
> kernel driver; Simple LMK seeks to replace that, at the very least until PSI and
> a userspace daemon utilizing PSI are ready for *all* Android devices, and not
> just the privileged Pixel phone line.

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