Re: [RFC PATCH v3 00/11] new cgroup controller for gpu/drm subsystem

Daniel Vetter
2019-07-02T13:21:44Z

On Sun, Jun 30, 2019 at 01:10:28AM -0400, Kenny Ho wrote:
> On Thu, Jun 27, 2019 at 3:24 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> > Another question I have: What about HMM? With the device memory zone
> > the core mm will be a lot more involved in managing that, but I also
> > expect that we'll have classic buffer-based management for a long time
> > still. So these need to work together, and I fear slightly that we'll
> > have memcg and drmcg fighting over the same pieces a bit perhaps?
> >
> > Adding Jerome, maybe he has some thoughts on this.
>
> I just did a bit of digging and this looks like the current behaviour:
> https://www.kernel.org/doc/html/v5.1/vm/hmm.html#memory-cgroup-memcg-and-rss-accounting
>
> "For now device memory is accounted as any regular page in rss
> counters (either anonymous if device page is used for anonymous, file
> if device page is used for file backed page or shmem if device page is
> used for shared memory). This is a deliberate choice to keep existing
> applications, that might start using device memory without knowing
> about it, running unimpacted.
>
> A drawback is that the OOM killer might kill an application using a
> lot of device memory and not a lot of regular system memory and thus
> not freeing much system memory. We want to gather more real world
> experience on how applications and system react under memory pressure
> in the presence of device memory before deciding to account device
> memory differently."

Hm ... I also just learned that the device memory stuff, at least the hmm
part, is probably getting removed again, and only the hmm_mirror part of
hmm will be kept. So maybe this doesn't matter to us. But really no idea.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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