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?