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

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Date:   Tue, 30 Jan 2018 11:28:55 +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 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.

-- 
Michal Hocko
SUSE Labs