Re: [PATCH] mm, memcg: cg2 memory{.swap,}.peak write handlers

[Michal Hocko <mhocko@suse.com>]

On Tue 16-07-24 10:00:10, Tejun Heo wrote:
> Hello,
> 
> On Tue, Jul 16, 2024 at 08:00:52PM +0200, Michal Hocko wrote:
> ...
> > > If we want to allow peak measurement of time periods, I wonder whether we
> > > could do something similar to pressure triggers - ie. let users register
> > > watchers so that each user can define their own watch periods. This is more
> > > involved but more useful and less error-inducing than adding reset to a
> > > single counter.
> > 
> > I would rather not get back to that unless we have many more users that
> > really need that. Absolute value of the memory consumption is a long
> > living concept that doesn't make much sense most of the time. People
> > just tend to still use it because it is much simpler to compare two different
> > values rather than something as dynamic as PSI similar metrics.
> 
> The initial justification for adding memory.peak was that it's mostly to
> monitor short lived cgroups. Adding reset would make it used more widely,
> which isn't necessarily a bad thing and people most likely will find ways to
> use it creatively. I'm mostly worried that that's going to create a mess
> down the road. Yeah, so, it's not widely useful now but adding reset makes
> it more useful and in a way which can potentially paint us into a corner.

I really fail to see how this would cause problems with future
maintainability. It is not like we are trying to deprecate this
memory.peak.

I am also not sure this makes it so much more attractive that people
would start using it just because they can reset the value. It makes
sense to extend our documentation and actually describe pitfalls.
-- 
Michal Hocko
SUSE Labs