On Fri 19-02-21 11:28:47, Tim Chen wrote: > > > 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 would rather drop it. The less the soft limit reclaim code is spread around the better. -- Michal Hocko SUSE Labs
