Re: [RFC 0/7] Introduce memory allocation speed throttle in memcg

[yulei zhang <yulei.kernel@gmail.com>]

On Thu, Jun 3, 2021 at 7:38 PM Chris Down <chris@chrisdown.name> wrote:
>
> yulei zhang writes:
> >Thanks. IMHO, there are differences between these two throttlings.
> >memory.high is a per-memcg throttle which targets to limit the memory
> >usage of the tasks in the cgroup. For the memory allocation speed throttle(MST),
> >the purpose is to avoid the memory burst in cgroup which would trigger
> >the global reclaim and affects the timing sensitive workloads in other cgroup.
> >For example, we have two pods with memory overcommit enabled, one includes
> >online tasks and the other has offline tasks, if we restrict the memory usage of
> >the offline pod with memory.high, it will lose the benefit of memory overcommit
> >when the other workloads are idle. On the other hand, if we don't
> >limit the memory
> >usage, it will easily break the system watermark when there suddenly has massive
> >memory operations. If enable MST in this case, we will be able to
> >avoid the direct
> >reclaim and leverage the overcommit.
>
> Having a speed throttle is a very primitive knob: it's hard to know what the
> correct values are for a user. That's one of the reasons why we've moved away
> from that kind of tunable for blkio.
>
> Ultimately, if you want work-conserving behaviour, why not use memory.low?

Thanks. But currently low and high are for cgroup v2 setting, do you
think we'd better
extend the same mechanism to cgroup v1?