From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jason Gunthorpe <jgg-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Subject: Re: [LSF/MM/BPF TOPIC] Reducing zombie memcgs
Date: Fri, 12 May 2023 18:09:20 -0300
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To: Alistair Popple <apopple-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Cc: Chris Li <chrisl-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, "T.J. Mercier" <tjmercier-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, lsf-pc-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Yosry Ahmed <yosryahmed-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Muchun Song <muchun.song-fxUVXftIFDnyG1zEObXtfA@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Roman Gushchin <roman.gushchin-fxUVXftIFDnyG1zEObXtfA@public.gmane.org>, Kalesh Singh <kaleshsingh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Yu Zhao <yuzhao-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>

On Fri, May 12, 2023 at 06:45:13PM +1000, Alistair Popple wrote:

> However review comments suggested it needed to be added as part of
> memcg. As soon as we do that we have to address how we deal with shared
> memory. If we stick with the original RLIMIT proposal this discussion
> goes away, but based on feedback I think I need to at least investigate
> integrating it into memcg to get anything merged.

Personally I don't see how we can effectively solve the per-page
problem without also tracking all the owning memcgs for every
page. This means giving each struct page an array of memcgs

I suspect this will be too expensive to be realistically
implementable.

If it is done then we may not even need a pin controller on its own as
the main memcg should capture most of it. (althought it doesn't
distinguish between movable/swappable and non-swappable memory)

But this is all being done for the libvirt people, so it would be good
to involve them

Jason