On Thu 11-04-19 20:41:32, Yafang Shao wrote: > On Thu, Apr 11, 2019 at 8:27 PM Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > > On Thu 11-04-19 19:59:51, Yafang Shao wrote: > > > The current item 'pgscan' is for pages in the memcg, > > > which indicates how many pages owned by this memcg are scanned. > > > While these pages may not scanned by the taskes in this memcg, even for > > > PGSCAN_DIRECT. > > > > > > Sometimes we need an item to indicate whehter the tasks in this memcg > > > under memory pressure or not. > > > So this new item allocstall is added into memory.stat. > > > > We do have memcg events for that purpose and those can even tell whether > > the pressure is a result of high or hard limit. Why is this not > > sufficient? > > > > The MEMCG_HIGH and MEMCG_LOW may not be tiggered by the tasks in this > memcg neither. > They all reflect the memory status of a memcg, rather than tasks > activity in this memcg. I do not follow. Can you give me an example when does this matter? I thought it is more important to see that there is a reclaim activity for a specific memcg as you account for that memcg. If you want to see/measure a reclaim imposed latency on a task then the counter doesn't make so much sense as you have no way to match that to a task. We have tracepoints for that purpose. -- Michal Hocko SUSE Labs
