Re: [PATCH 0/2] memcg, vmpressure: expose vmpressure controls

[Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

On Tue 14-04-20 18:12:47, Leonid Moiseichuk wrote:
> I do not agree with all comments, see below.
> 
> On Tue, Apr 14, 2020 at 3:23 PM Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org> wrote:
> 
> > On Tue, Apr 14, 2020 at 12:42:44PM -0400, Leonid Moiseichuk wrote:
> > > On Tue, Apr 14, 2020 at 7:37 AM Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> wrote:
> > > > On Mon 13-04-20 17:57:48, svc_lmoiseichuk-baZASSJvGmz3oGB3hsPCZA@public.gmane.org wrote:
> > > > Anyway, I have to confess I am not a big fan of this. vmpressure turned
> > > > out to be a very weak interface to measure the memory pressure. Not
> > only
> > > > it is not numa aware which makes it unusable on many systems it also
> > > > gives data way too late from the practice.
> >
> > Yes, it's late in the game for vmpressure, and also a bit too late for
> > extensive changes in cgroup1.
> >
> 200 lines just to move functionality from one place to another without
> logic change?
> There does not seem to be extensive changes.

Any user visible API is an big change. We have to maintain any api for
ever. So there has to be a really strong reason/use case for inclusion.
I haven't heard any strong justification so far. It all seems to me that
you are trying to workaround real vmpressure issues by fine tunning
parameters and that is almost always a bad reason for a adding a new
tunning.
-- 
Michal Hocko
SUSE Labs