On Fri, 23 Mar 2018 18:20:28 +0300 Andrey Ryabinin <aryabi...@virtuozzo.com> wrote:
> We have separate LRU list for each memory cgroup. Memory reclaim iterates > over cgroups and calls shrink_inactive_list() every inactive LRU list. > Based on the state of a single LRU shrink_inactive_list() may flag > the whole node as dirty,congested or under writeback. This is obviously > wrong and hurtful. It's especially hurtful when we have possibly > small congested cgroup in system. Than *all* direct reclaims waste time > by sleeping in wait_iff_congested(). And the more memcgs in the system > we have the longer memory allocation stall is, because > wait_iff_congested() called on each lru-list scan. > > Sum reclaim stats across all visited LRUs on node and flag node as dirty, > congested or under writeback based on that sum. Also call > congestion_wait(), wait_iff_congested() once per pgdat scan, instead of > once per lru-list scan. > > This only fixes the problem for global reclaim case. Per-cgroup reclaim > may alter global pgdat flags too, which is wrong. But that is separate > issue and will be addressed in the next patch. > > This change will not have any effect on a systems with all workload > concentrated in a single cgroup. > Could we please get this reviewed?
