| Message ID | 20230328221644.803272-4-yosryahmed@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | memcg: make rstat flushing irq and sleep | expand |
On Tue 28-03-23 22:16:38, Yosry Ahmed wrote: > Currently, the only context in which we can invoke an rstat flush from > irq context is through mem_cgroup_usage() on the root memcg when called > from memcg_check_events(). An rstat flush is an expensive operation that > should not be done in irq context, so do not flush stats and use the > stale stats in this case. > > Arguably, usage threshold events are not reliable on the root memcg > anyway since its usage is ill-defined. > > Suggested-by: Johannes Weiner <hannes@cmpxchg.org> > Suggested-by: Shakeel Butt <shakeelb@google.com> > Signed-off-by: Yosry Ahmed <yosryahmed@google.com> > Acked-by: Shakeel Butt <shakeelb@google.com> > Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/memcontrol.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index c3b6aae78901..ff39f78f962e 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3669,7 +3669,21 @@ static unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap) > unsigned long val; > > if (mem_cgroup_is_root(memcg)) { > - mem_cgroup_flush_stats(); > + /* > + * We can reach here from irq context through: > + * uncharge_batch() > + * |--memcg_check_events() > + * |--mem_cgroup_threshold() > + * |--__mem_cgroup_threshold() > + * |--mem_cgroup_usage > + * > + * rstat flushing is an expensive operation that should not be > + * done from irq context; use stale stats in this case. > + * Arguably, usage threshold events are not reliable on the root > + * memcg anyway since its usage is ill-defined. > + */ > + if (in_task()) > + mem_cgroup_flush_stats(); > val = memcg_page_state(memcg, NR_FILE_PAGES) + > memcg_page_state(memcg, NR_ANON_MAPPED); > if (swap) > -- > 2.40.0.348.gf938b09366-goog
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c3b6aae78901..ff39f78f962e 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3669,7 +3669,21 @@ static unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap) unsigned long val; if (mem_cgroup_is_root(memcg)) { - mem_cgroup_flush_stats(); + /* + * We can reach here from irq context through: + * uncharge_batch() + * |--memcg_check_events() + * |--mem_cgroup_threshold() + * |--__mem_cgroup_threshold() + * |--mem_cgroup_usage + * + * rstat flushing is an expensive operation that should not be + * done from irq context; use stale stats in this case. + * Arguably, usage threshold events are not reliable on the root + * memcg anyway since its usage is ill-defined. + */ + if (in_task()) + mem_cgroup_flush_stats(); val = memcg_page_state(memcg, NR_FILE_PAGES) + memcg_page_state(memcg, NR_ANON_MAPPED); if (swap)