On Thu, Mar 30, 2023 at 12:52 AM Michal Hocko <mhocko@xxxxxxxx> wrote: > > On Thu 30-03-23 00:44:10, Yosry Ahmed wrote: > > On Thu, Mar 30, 2023 at 12:40 AM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > > > On Tue 28-03-23 22:16:43, Yosry Ahmed wrote: > > > > Memory reclaim is a sleepable context. Allow sleeping when flushing > > > > memcg stats to avoid unnecessarily performing a lot of work without > > > > sleeping. This can slow down reclaim code if flushing stats is taking > > > > too long, but there is already multiple cond_resched()'s in reclaim > > > > code. > > > > > > Why is this preferred? Memory reclaim is surely a slow path but what is > > > the advantage of calling mem_cgroup_flush_stats here? > > > > The purpose of this series is to limit calls to atomic flushing as > > much as possible, as flushing can become really expensive on systems > > with high cpu counts and a lot of cgroups, and performing such an > > expensive operation atomically causes problems -- so we'd rather avoid > > doing it atomically where possible. > > Please add that to the changelog. While the intention might be obvious > now (although cover is not explicit about it either) it can cause some > head scratching in the future when somebody looks at this commit without > a broader context (e.g. previous ML discussions). > > with that > Acked-by: Michal Hocko <mhocko@xxxxxxxx> Thanks, will do for the respin. > Thanks > > > > > Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx> > > > > Acked-by: Shakeel Butt <shakeelb@xxxxxxxxxx> > > > > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> > > > > --- > > > > mm/vmscan.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > > > index a9511ccb936f..9c1c5e8b24b8 100644 > > > > --- a/mm/vmscan.c > > > > +++ b/mm/vmscan.c > > > > @@ -2845,7 +2845,7 @@ static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc) > > > > * Flush the memory cgroup stats, so that we read accurate per-memcg > > > > * lruvec stats for heuristics. > > > > */ > > > > - mem_cgroup_flush_stats_atomic(); > > > > + mem_cgroup_flush_stats(); > > > > > > > > /* > > > > * Determine the scan balance between anon and file LRUs. > > > > -- > > > > 2.40.0.348.gf938b09366-goog > > > > > > -- > > > Michal Hocko > > > SUSE Labs > > -- > Michal Hocko > SUSE Labs
