On Tue, Sep 22, 2020 at 6:42 PM Chris Down <chris@xxxxxxxxxxxxxx> wrote: > > Chunxin Zang writes: > >On Tue, Sep 22, 2020 at 5:51 PM Chris Down <chris@xxxxxxxxxxxxxx> wrote: > >> > >> 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? > > > >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. Please forgive me for not being able to understand why setting memory.low for Type_A can solve the problem. In my scene, Type_A is the most important, so I will set 100G to memory.low. But 'memory.low' only takes effect passively when the kernel is reclaiming memory. It means that reclaim Type_B's memory only when Type_A in alloc memory slow path. This will affect Type_A's performance. We want to reclaim Type_B's memory in advance when A is expected to be busy. Best wishes Chunxin
