On Wed, Aug 21, 2019 at 4:34 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > On Wed 21-08-19 16:15:54, Yafang Shao wrote: > > On Wed, Aug 21, 2019 at 4:05 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > > > On Wed 21-08-19 15:26:56, Yafang Shao wrote: > > > > On Wed, Aug 21, 2019 at 2:44 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > > > > > > > On Wed 21-08-19 09:00:39, Yafang Shao wrote: > > > > > [...] > > > > > > More possible OOMs is also a strong side effect (and it prevent us > > > > > > from using it). > > > > > > > > > > So why don't you use low limit if the guarantee side of min limit is too > > > > > strong for you? > > > > > > > > Well, I don't know what the best-practice of memory.min is. > > > > > > It is really a workload reclaim protection. Say you have a memory > > > consumer which performance characteristics would be noticeably disrupted > > > by any memory reclaim which then would lead to SLA disruption. This is a > > > strong requirement/QoS feature and as such comes with its demand on > > > configuration. > > > > > > > In our plan, we want to use it to protect the top priority containers > > > > (e.g. set the memory.min same with memory limit), which may latency > > > > sensive. Using memory.min may sometimes decrease the refault. > > > > If we set it too low, it may useless, becasue what memory.min is > > > > protecting is not specified. And if there're some busrt anon memory > > > > allocate in this memcg, the memory.min may can't protect any file > > > > memory. > > > > > > I am still not seeing why you are considering guarantee (memory.min) > > > rather than best practice (memory.low) here? > > > > Let me show some examples for you. > > Suppose we have three containers with different priorities, which are > > high priority, medium priority and low priority. > > Then we set memory.low to these containers as bellow, > > high prioirty: memory.low same with memory.max > > medium priroity: memory.low is 50% of memory.max > > low priority: memory.low is 0 > > > > When all relcaimable pages withouth protection are reclaimed, the > > reclaimer begins to reclaim the protected pages, but unforuantely it > > desn't know which pages are belonging to high priority container and > > which pages are belonging to medium priority container. So the > > relcaimer may reclaim the high priority contianer first, and without > > reclaiming the medium priority container at all. > > Hmm, it is hard to comment on this configuration without knowing what is > the overall consumption of all the three. In any case reclaiming all of > the reclaimable memory means that you have actually reclaimed full of > the low and half of the medium container to even start hitting on high > priority one. When there are only low priority protected containers then > they will get reclaimed proportionally to their size. Right. I think priority-based reclaimer (different priorities has differecnt proportional scan count ) would be more fine, while memroy.low is not easy to practice in this situation. Thanks Yafang
