Re: [PATCH] ipc: remove memcg accounting for sops objects in do_semtimedop()

[Michal Hocko]

On Mon 13-09-21 21:32:25, Shakeel Butt wrote:
> On Mon, Sep 13, 2021 at 1:37 AM Michal Hocko <mhocko@xxxxxxxx> wrote:
> >
> [...]
> > > However Shakeel Butt pointed that there are much more popular objects
> > > with the same life time and similar memory consumption, the accounting
> > > of which was decided to be rejected for performance reasons.
> >
> > Is there any measurable performance impact in this particular case?
> >
> 
> I don't think there was any regression report or any performance
> evaluation. Linus raised the concern on the potential performance
> impact. I suggested to backoff for this allocation for now and revisit
> again once we have improved the memcg accounting for kernel memory.

I am fine with the change, I am just not satisfied with the
justification. It is not really clear what the intention is except that
Linus wanted it. I have already asked Vasily to provide more
explanation. E.g. this part really begs for clarification
"
This object can consume up to 2 pages, syscall is sleeping one,
size and duration can be controlled by user, and this allocation
can be repeated by many thread at the same time.
"

It sounds like a problem, except it is not because? A worst case
scenario evaluation would be beneficial for example

Thanks!

-- 
Michal Hocko
SUSE Labs