On Wed 20-10-21 19:45:33, Zhaoyang Huang wrote: > On Wed, Oct 20, 2021 at 4:55 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > On Wed 20-10-21 15:33:39, Zhaoyang Huang wrote: > > [...] > > > Do you mean that direct reclaim should succeed for the first round > > > reclaim within which memcg get protected by memory.low and would NOT > > > retry by setting memcg_low_reclaim to true? > > > > Yes, this is the semantic of low limit protection in the upstream > > kernel. Have a look at do_try_to_free_pages and how it sets > > memcg_low_reclaim only if there were no pages reclaimed. > > > > > It is not true in android > > > like system, where reclaim always failed and introduce lmk and even > > > OOM. > > > > I am not familiar with android specific changes to the upstream reclaim > > logic. You should be investigating why the reclaim couldn't make a > > forward progress (aka reclaim pages) from non-protected memcgs. There > > are tracepoints you can use (generally vmscan prefix). > Ok, I am aware of why you get confused now. I think you are analysing > cgroup's behaviour according to a pre-defined workload and memory > pattern, which should work according to the design, such as processes > within root should provide memory before protected memcg get > reclaimed. You can refer [1] as the hierarchy, where effective > userspace workloads locate in protect groups and have rest of > processes be non-grouped. In fact, non-grouped ones can not provide > enough memory as they are kernel threads and the processes with few > pages on LRU(control logic inside). The practical scenario is groupA > launched a high-order kmalloc and introduce reclaiming(kswapd and > direct reclaim). As I said, non-grouped ones can not provide enough > contiguous memory blocks which let direct reclaim quickly fail for the > first round reclaiming. What I am trying to do is that let kswapd try > more for the target. It is also fair if groupA,B,C are trapping in > slow path concurrently. > > [1] > root > | | > | | > non-grouped processes groupA groupB groupC I am sorry but I still do not understand your setup. I have asked several times for more specifics. Without that I cannot really wrap my head around your (ever changing) statements. This is not really a productive use of time. I am sorry but I cannot really help you much without understanding the actual problem. -- Michal Hocko SUSE Labs
