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

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Date:   Tue, 30 Jan 2018 11:48:06 +0100
From:   Michel Dänzer <michel@...nzer.net>
To:     christian.koenig@....com, Michal Hocko <mhocko@...nel.org>,
        Roman Gushchin <guro@...com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, amd-gfx@...ts.freedesktop.org
Subject: Re: [RFC] Per file OOM badness

On 2018-01-30 11:42 AM, Daniel Vetter wrote:
> On Tue, Jan 30, 2018 at 10:43:10AM +0100, Michel Dänzer wrote:
>> On 2018-01-30 10:31 AM, Daniel Vetter wrote:
>>
>>> I guess a good first order approximation would be if we simply charge any
>>> newly allocated buffers to the process that created them, but that means
>>> hanging onto lots of mm_struct pointers since we want to make sure we then
>>> release those pages to the right mm again (since the process that drops
>>> the last ref might be a totally different one, depending upon how the
>>> buffers or DRM fd have been shared).
>>>
>>> Would it be ok to hang onto potentially arbitrary mmget references
>>> essentially forever? If that's ok I think we can do your process based
>>> account (minus a few minor inaccuracies for shared stuff perhaps, but no
>>> one cares about that).
>>
>> Honestly, I think you and Christian are overthinking this. Let's try
>> charging the memory to every process which shares a buffer, and go from
>> there.
> 
> I'm not concerned about wrongly accounting shared buffers (they don't
> matter), but imbalanced accounting. I.e. allocate a buffer in the client,
> share it, but then the compositor drops the last reference.

I don't think the order matters. The memory is "uncharged" in each
process when it drops its reference.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer