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

[Chris Down <chris-6Bi1550iOqEnzZ6mRAm98g@public.gmane.org>]

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?