On Fri, May 6, 2022 at 1:50 PM Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > On Fri, May 06, 2022 at 08:56:31AM -0700, Shakeel Butt wrote: > > On Fri, May 6, 2022 at 7:57 AM Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > > > > > On Thu, May 05, 2022 at 05:13:30AM -0700, Ganesan Rajagopal wrote: > > > > v1 memcg exports memcg->watermark as "memory.mem_usage_in_bytes" in > > > > sysfs. This is missing for v2 memcg though "memory.current" is exported. > > > > There is no other easy way of getting this information in Linux. > > > > getrsuage() returns ru_maxrss but that's the max RSS of a single process > > > > instead of the aggregated max RSS of all the processes. Hence, expose > > > > memcg->watermark as "memory.watermark" for v2 memcg. > > > > > > > > Signed-off-by: Ganesan Rajagopal <rganesan@xxxxxxxxxx> > > > > > > This wasn't initially added to cgroup2 because its usefulness is very > > > specific: it's (mostly) useless on limited cgroups, on long-running > > > cgroups, and on cgroups that are recycled for multiple jobs. And I > > > expect these categories apply to the majority of cgroup usecases. > > > > > > However, for the situation where you want to measure the footprint of > > > a short-lived, unlimited one-off cgroup, there really is no good > > > alternative. And it's a legitimate usecase. It doesn't cost much to > > > maintain this info. So I think we should go ahead with this patch. > > > > > > But please add a blurb to Documentation/admin-guide/cgroup-v2.rst. > > > > No objection from me. I do have two points: (1) watermark is not a > > good name for this interface, maybe max_usage or something. > > How about memory.peak? It'd be nice to avoid underscores. > > > (2) a way to reset (i.e. write to it, reset it). > > We used to have that with cgroup1, but it gets weird in modern cgroup > environments when there can be multiple consumers. One of them resets > the stat for their own purpose, now the others have no idea what > sample time frame they are looking at. > > It'd be more robust if we just said "peak usage since birth of > cgroup". If you want to sample new work, create a new cgroup. SGTM for both.
