Re: [PATCH] mm/memcg: support control THP behaviour in cgroup

[Roman Gushchin]

On Tue, May 10, 2022 at 07:47:29PM -0700, Shakeel Butt wrote:
> On Tue, May 10, 2022 at 7:19 PM CGEL <cgel.zte@xxxxxxxxx> wrote:
> >
> [...]
> > > > >
> > > > > All controls in cgroup v2 should be hierarchical. This is really
> > > > > required for a proper delegation semantic.
> > > > >
> > > >
> > > > Could we align to the semantic of /sys/fs/cgroup/memory.swappiness?
> > > > Some distributions like Ubuntu is still using cgroup v1.
> > >
> > > Other than enable flag, how would you handle the defrag flag
> > > hierarchically? It is much more complicated.
> >
> > Refer to memory.swappiness for cgroup, this new interface better be independent.
> 
> Let me give my 0.02. I buy the use-case of Admin restricting THPs to
> low priority jobs but I don't think memory controller is the right
> place to enforce that policy. Michal gave one way (prctl()) to enforce
> that policy. Have you explored the BPF way to enforce this policy?

+1 for bpf

I think these THP hints are too implementation-dependent and unstable to become
a part of cgroup API.

Thanks!