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charset=us-ascii Content-Disposition: inline In-Reply-To: <20230328221644.803272-4-yosryahmed@google.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: E7E8710000C X-Stat-Signature: pmyqo3tsekpimutigxxw7hx6iqwo7tiu X-Rspam-User: X-HE-Tag: 1680091124-450958 X-HE-Meta: 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 XCeSt1mp z2SPfbGGbU2G+p6BvhSAlkBYKu8jKZhIdvyd267KLchGypes+9u95B4NXMcObZHb/jTO8thR8bOQ72MNDwvOG9e8pSaWerWt5w5pwxxYoGIgagSgV6pfb6PrgNKXJmYHdtuwRGFeBVBdu6iuEtzDlIe4LaBUDyS137d50Ol0cvXr+A2QGUhN3JaxpwXIyYGzWwL+M9mUFqUJJNGYFNYjkaQQlBuckc3HGplLGdP8EokWv8FF02Tn9CQ6hNve+w/9cDZIYV2smOy3TCrrwMW1nkRrrI4mCbF27xEZeFqxqCxtavkpFHj3moYN32A== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 > Suggested-by: Shakeel Butt > Signed-off-by: Yosry Ahmed > Acked-by: Shakeel Butt > Acked-by: Johannes Weiner Acked-by: Michal Hocko > --- > 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 -- Michal Hocko SUSE Labs