On 2/19/21 1:16 AM, Michal Hocko wrote: >> >> Something like this? >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 8bddee75f5cb..b50cae3b2a1a 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -3472,6 +3472,14 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order, >> if (!mz) >> break; >> >> + /* >> + * Soft limit tree is updated based on memcg events sampling. >> + * We could have missed some updates on page uncharge and >> + * the cgroup is below soft limit. Skip useless soft reclaim. >> + */ >> + if (!soft_limit_excess(mz->memcg)) >> + continue; >> + >> nr_scanned = 0; >> reclaimed = mem_cgroup_soft_reclaim(mz->memcg, pgdat, > > Yes I meant something like this but then I have looked more closely and > this shouldn't be needed afterall. __mem_cgroup_largest_soft_limit_node > already does all the work > if (!soft_limit_excess(mz->memcg) || > !css_tryget(&mz->memcg->css)) > goto retry; > so this shouldn't really happen. > Ah, that's true. The added check for soft_limit_excess is not needed. Do you think it is still a good idea to add patch 3 to restrict the uncharge update in page batch of the same node and cgroup? I am okay with dropping patch 3 and let the inaccuracies in the ordering of soft limit tree be cleared out by an occasional soft reclaim. These inaccuracies will still be there even with patch 3 fix due to the memcg event sampling. Patch 3 does help to keep the soft reclaim tree ordering more up to date. Thanks. Tim
