On Fri, May 17, 2019 at 05:18:18PM -0700, Shakeel Butt wrote: > The memory controller in cgroup v2 exposes memory.events file for each > memcg which shows the number of times events like low, high, max, oom > and oom_kill have happened for the whole tree rooted at that memcg. > Users can also poll or register notification to monitor the changes in > that file. Any event at any level of the tree rooted at memcg will > notify all the listeners along the path till root_mem_cgroup. There are > existing users which depend on this behavior. > > However there are users which are only interested in the events > happening at a specific level of the memcg tree and not in the events in > the underlying tree rooted at that memcg. One such use-case is a > centralized resource monitor which can dynamically adjust the limits of > the jobs running on a system. The jobs can create their sub-hierarchy > for their own sub-tasks. The centralized monitor is only interested in > the events at the top level memcgs of the jobs as it can then act and > adjust the limits of the jobs. Using the current memory.events for such > centralized monitor is very inconvenient. The monitor will keep > receiving events which it is not interested and to find if the received > event is interesting, it has to read memory.event files of the next > level and compare it with the top level one. So, let's introduce > memory.events.local to the memcg which shows and notify for the events > at the memcg level. > > Now, does memory.stat and memory.pressure need their local versions. > IMHO no due to the no internal process contraint of the cgroup v2. The > memory.stat file of the top level memcg of a job shows the stats and > vmevents of the whole tree. The local stats or vmevents of the top level > memcg will only change if there is a process running in that memcg but > v2 does not allow that. Similarly for memory.pressure there will not be > any process in the internal nodes and thus no chance of local pressure. > > Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx> This looks reasonable to me. Thanks for working out a clear use case and also addressing how it compares to the stats and pressure files. Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
