[now CC Vladimir for real] On Tue 04-09-18 20:06:31, Michal Hocko wrote: > On Tue 04-09-18 10:52:46, Roman Gushchin wrote: > > On Tue, Sep 04, 2018 at 06:14:31PM +0200, Michal Hocko wrote: > [...] > > > I am not opposing your patch but I am trying to figure out whether that > > > is the best approach. > > > > I don't think the current logic does make sense. Why should cgroups > > with less than 4k kernel objects be excluded from being scanned? > > How is it any different from the the LRU reclaim? Maybe it is just not > that visible because there usually more pages there. But in principle it > is the same issue AFAICS. > > > Reparenting of all pages is definitely an option to consider, > > but it's not free in any case, so if there is no problem, > > why should we? Let's keep it as a last measure. In my case, > > the proposed patch works perfectly: the number of dying cgroups > > jumps around 100, where it grew steadily to 2k and more before. > > Let me emphasise that I am not opposing the patch. I just think that we > have made some decisions which are not ideal but I would really like to > prevent from building workarounds on top. If we have to reconsider some > of those decisions then let's do it. Maybe the priority scaling is just > too coarse and what seem to work work for normal LRUs doesn't work for > shrinkers. > > > I believe that reparenting of LRU lists is required to minimize > > the number of LRU lists to scan, but I'm not sure. > > Well, we do have more lists to scan for normal LRUs. It is true that > shrinkers add multiplining factor to that but in principle I guess we > really want to distinguish dead memcgs because we do want to reclaim > those much more than the rest. Those objects are basically of no use > just eating resources. The pagecache has some chance to be reused at > least but I fail to see why we should keep kernel objects around. Sure, > some of them might be harder to reclaim due to different life time and > internal object management but this doesn't change the fact that we > should try hard to reclaim those. So my gut feeling tells me that we > should have a way to distinguish them. > > Btw. I do not see Vladimir on the CC list. Added (the thread starts > here http://lkml.kernel.org/r/20180831203450.2536-1-guro@xxxxxx) -- Michal Hocko SUSE Labs
