On Fri, Jul 03, 2020 at 07:23:14AM -0700, Shakeel Butt wrote: > On Thu, Jul 2, 2020 at 11:35 PM Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > > On Thu 02-07-20 08:22:22, Shakeel Butt wrote: > > [...] > > > Interface options: > > > ------------------ > > > > > > 1) memcg interface e.g. 'echo 10M > memory.reclaim' > > > > > > + simple > > > + can be extended to target specific type of memory (anon, file, kmem). > > > - most probably restricted to cgroup v2. > > > > > > 2) fadvise(PAGEOUT) on cgroup_dir_fd > > > > > > + more general and applicable to other FSes (actually we are using > > > something similar for tmpfs). > > > + can be extended in future to just age the LRUs instead of reclaim or > > > some new use cases. > > > > Could you explain why memory.high as an interface to trigger pro-active > > memory reclaim is not sufficient. Also memory.low limit to protect > > latency sensitve workloads? I initially liked the proposal, but after some thoughts I've realized that I don't know a good use case where memory.high is less useful. Shakeel, what's the typical use case you thinking of? Who and how will use the new interface? > > Yes, we can use memory.high to trigger [proactive] reclaim in a memcg > but note that it can also introduce stalls in the application running > in that memcg. Let's suppose the memory.current of a memcg is 100MiB > and we want to reclaim 20MiB from it, we can set the memory.high to > 80MiB but any allocation attempt from the application running in that > memcg can get stalled/throttled. I want the functionality of the > reclaim without potential stalls. But reclaiming some pagecache/swapping out anon pages can always generate some stalls caused by pagefaults, no? Thanks!
