linux-kernel - Re: [RFC] Per file OOM badness

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Message-ID: <1522074988.1196.1.camel@pengutronix.de>
Date:   Mon, 26 Mar 2018 16:36:28 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Michal Hocko <mhocko@...nel.org>,
        Michel Dänzer <michel@...nzer.net>
Cc:     linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        Christian.Koenig@....com, linux-mm@...ck.org,
        dri-devel@...ts.freedesktop.org, Roman Gushchin <guro@...com>
Subject: Re: [RFC] Per file OOM badness

Hi all,

Am Dienstag, den 30.01.2018, 11:28 +0100 schrieb Michal Hocko:
> On Tue 30-01-18 10:29:10, Michel Dänzer wrote:
> > On 2018-01-24 12:50 PM, Michal Hocko wrote:
> > > On Wed 24-01-18 12:23:10, Michel Dänzer wrote:
> > > > On 2018-01-24 12:01 PM, Michal Hocko wrote:
> > > > > On Wed 24-01-18 11:27:15, Michel Dänzer wrote:
> > > 
> > > [...]
> > > > > > 2. If the OOM killer kills a process which is sharing BOs
> > > > > > with another
> > > > > > process, this should result in the other process dropping
> > > > > > its references
> > > > > > to the BOs as well, at which point the memory is released.
> > > > > 
> > > > > OK. How exactly are those BOs mapped to the userspace?
> > > > 
> > > > I'm not sure what you're asking. Userspace mostly uses a GEM
> > > > handle to
> > > > refer to a BO. There can also be userspace CPU mappings of the
> > > > BO's
> > > > memory, but userspace doesn't need CPU mappings for all BOs and
> > > > only
> > > > creates them as needed.
> > > 
> > > OK, I guess you have to bear with me some more. This whole stack
> > > is a
> > > complete uknonwn. I am mostly after finding a boundary where you
> > > can
> > > charge the allocated memory to the process so that the oom killer
> > > can
> > > consider it. Is there anything like that? Except for the proposed
> > > file
> > > handle hack?
> > 
> > How about the other way around: what APIs can we use to charge /
> > "uncharge" memory to a process? If we have those, we can experiment
> > with
> > different places to call them.
> 
> add_mm_counter() and I would add a new counter e.g. MM_KERNEL_PAGES.

So is anyone still working on this? This is hurting us bad enough that
I don't want to keep this topic rotting for another year.

If no one is currently working on this I would volunteer to give the
simple "just account private, non-shared buffers in process RSS" a
spin.

Regards,
Lucas