Chunxin Zang writes:

On Tue, Sep 22, 2020 at 5:51 PM Chris Down [off-list ref] wrote:

quoted

Chunxin Zang writes:

quoted

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?

But we cannot estimate how much memory Type_A uses at least.

memory.low allows ballparking, you don't have to know exactly how much it uses.  
Any amount of protection biases reclaim away from that cgroup.

For example:
total memory: 100G
At the beginning, Type_A was in an idle state, and it only used 10G of memory.
The load is very low. We want to run Type_B to avoid wasting machine resources.
When Type_B runs for a while, it used 80G of memory.
At this time Type_A is busy, it needs more memory.

Ok, so set memory.low for Type_A close to your maximum expected value.