Subject: Re: [External] Re: [PATCH] mm/memcontrol: Add the drop_cache interface for cgroup v2

From: Chris Down <[email-masked]>
Date: Tue, 22 Sep 2020 10:51:36 +0100

Chunxin Zang writes:
>My usecase is that there are two types of services in one server. They
>have difference
>priorities. Type_A has the highest priority, we need to ensure it's
>schedule latency、I/O
>latency、memory enough. Type_B has the lowest priority, we expect it
>will not affect
>Type_A when executed.
>So Type_A could use memory without any limit. Type_B could use memory
>only when the
>memory is absolutely sufficient. But we cannot estimate how much
>memory Type_B should
>use. Because everything is dynamic. So we can't set Type_B's memory.high.
>
>So we want to release the memory of Type_B when global memory is
>insufficient in order
>to ensure the quality of service of Type_A . In the past, we used the
>'force_empty' interface
>of cgroup v1.

This sounds like a perfect use case for memory.low on Type_A, and it's pretty 
much exactly what we invented it for. What's the problem with that?