On Tue 24-11-20 13:27:32, Aaron Tomlin wrote: > On Tue, 24 Nov 2020 at 11:26, Michal Hocko <mhocko@xxxxxxxx> wrote: > > > On Tue 24-11-20 10:58:36, Aaron Tomlin wrote: > > > Each memory-controlled cgroup is assigned a unique ID and the total > > > number of memory cgroups is limited to MEM_CGROUP_ID_MAX. > > > > > > This patch provides the ability to determine the number of > > > memory cgroups from the root memory cgroup, only. > > > A value of 1 (i.e. self count) is returned if there are no children. > > > For example, the number of memory cgroups can be established by > > > reading the /sys/fs/cgroup/memory/memory.total_cnt file. > > > > Hi Michal, > > > > Could you add some explanation why is this information useful for > > userspace? Who is going to use it and why a simple scripting on top of > > cgroupfs is insufficient. > > > > Thank you for your feedback. > > Indeed, one can use a command/script to manually calculate this. > Having said that, one that creates a significant number of > memory-controlled cgroups may prefer a quick, simple and reliable method > to generate the aforementioned data, for management purposes only. > As such, I thought this patch might be particularly useful. This like any other user visible interface would be a much easier sell if there was a clear usecase to justify it. I do not see anything controversial about exporting such a value but my general take is that we are only adding new interface when existing ones are insufficient. A performance might be a very good reason but that would really require to come with some real life numbers. Thanks! -- Michal Hocko SUSE Labs
