Re: [PATCH v4 3/4] mm: memcg: let non-unified root stats flushes help unified flushes

Michal Hocko
2023-09-04T15:41:15Z

On Mon 04-09-23 17:29:14, Michal Koutny wrote:
> Hello.
>
> On Mon, Sep 04, 2023 at 04:50:15PM +0200, Michal Hocko <mhocko@suse.com> wrote:
> > I have hard time to follow why we really want/need this. Does this cause
> > any observable changes to the behavior?
>
> Behavior change depends on how much userspace triggers the root memcg
> flush, from nothing to effectively offloading flushing to userspace tasks.
> (Theory^^^)
>
> It keeps stats_flush_threshold up to date representing global error
> estimate so that error-tolerant readers may save their time and it keeps
> the reasoning about the stats_flush_threshold effect simple.

So it also creates an undocumented but userspace visible behavior.
Something that userspace might start depending on, right?
--
Michal Hocko
SUSE Labs