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

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Message-ID: <20180124110141.GA28465@dhcp22.suse.cz>
Date:   Wed, 24 Jan 2018 12:01:41 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Michel Dänzer <michel@...nzer.net>
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Christian.Koenig@....com, linux-mm@...ck.org,
        amd-gfx@...ts.freedesktop.org, Roman Gushchin <guro@...com>
Subject: Re: [RFC] Per file OOM badness

On Wed 24-01-18 11:27:15, Michel Dänzer wrote:
> On 2018-01-24 10:28 AM, Michal Hocko wrote:
[...]
> > So how exactly then helps to kill one of those processes? The memory
> > stays pinned behind or do I still misunderstand?
> 
> Fundamentally, the memory is only released once all references to the
> BOs are dropped. That's true no matter how the memory is accounted for
> between the processes referencing the BO.
> 
> 
> In practice, this should be fine:
> 
> 1. The amount of memory used for shared BOs is normally small compared
> to the amount of memory used for non-shared BOs (and other things). So
> regardless of how shared BOs are accounted for, the OOM killer should
> first target the process which is responsible for more memory overall.

OK. So this is essentially the same as with the normal shared memory
which is a part of the RSS in general.

> 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?
-- 
Michal Hocko
SUSE Labs