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?
