Re: [LSF/MM/BPF TOPIC] Reducing zombie memcgs

[Jason Gunthorpe <jgg-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On Sat, May 20, 2023 at 08:31:01AM -0700, Chris Li wrote:
> > This is basically where we need to get everyone aligned. The RLIMIT
> > approach currently implemented by my patch series does (2). For example:
> > 
> > 1. If a process in a pincg requests (eg. via driver ioctl) to pin a page
> >    it is charged against the pincg limit and will fail if going over
> >    limit.
> > 
> > 2. If the same process requests another pin (doesn't matter if it's the
> >    same page or not) it will be charged again and can't go over limit.
> > 
> > 3. If another process in the same pincg requests a page (again, doesn't
> >    matter if it's the same page or not) be pinned it will be charged
> >    against the limit.
> 
> I see. You want to track and punish the number of time process
> issue pin ioctl on the page.

Yes, because it is feasible to count that without a lot of overhead

In a perfect world each cgroup would be charged exactly once while any
pin is active regardless of how many times something in the cgroup
caused it to be pinned	.

Jason