From: Yosry Ahmed <yosryahmed@google.com> To: "Tejun Heo" <tj@kernel.org>, "Josef Bacik" <josef@toxicpanda.com>, "Jens Axboe" <axboe@kernel.dk>, "Zefan Li" <lizefan.x@bytedance.com>, "Johannes Weiner" <hannes@cmpxchg.org>, "Michal Hocko" <mhocko@kernel.org>, "Roman Gushchin" <roman.gushchin@linux.dev>, "Shakeel Butt" <shakeelb@google.com>, "Muchun Song" <muchun.song@linux.dev>, "Andrew Morton" <akpm@linux-foundation.org>, "Michal Koutný" <mkoutny@suse.com> Cc: Vasily Averin <vasily.averin@linux.dev>, cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, Yosry Ahmed <yosryahmed@google.com>, Michal Hocko <mhocko@suse.com> Subject: [PATCH v3 3/8] memcg: do not flush stats in irq context Date: Thu, 30 Mar 2023 19:17:56 +0000 [thread overview] Message-ID: <20230330191801.1967435-4-yosryahmed@google.com> (raw) In-Reply-To: <20230330191801.1967435-1-yosryahmed@google.com> 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
WARNING: multiple messages have this Message-ID (diff)
From: Yosry Ahmed <yosryahmed-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> To: "Tejun Heo" <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, "Josef Bacik" <josef-DigfWCa+lFGyeJad7bwFQA@public.gmane.org>, "Jens Axboe" <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>, "Zefan Li" <lizefan.x-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>, "Johannes Weiner" <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, "Michal Hocko" <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, "Roman Gushchin" <roman.gushchin-fxUVXftIFDnyG1zEObXtfA@public.gmane.org>, "Shakeel Butt" <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, "Muchun Song" <muchun.song-fxUVXftIFDnyG1zEObXtfA@public.gmane.org>, "Andrew Morton" <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, "Michal Koutný" <mkoutny-IBi9RG/b67k@public.gmane.org> Cc: Vasily Averin <vasily.averin-fxUVXftIFDnyG1zEObXtfA@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, bpf-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Yosry Ahmed <yosryahmed-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org> Subject: [PATCH v3 3/8] memcg: do not flush stats in irq context Date: Thu, 30 Mar 2023 19:17:56 +0000 [thread overview] Message-ID: <20230330191801.1967435-4-yosryahmed@google.com> (raw) In-Reply-To: <20230330191801.1967435-1-yosryahmed-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> 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-druUgvl0LCNAfugRpC6u6w@public.gmane.org> Suggested-by: Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> Signed-off-by: Yosry Ahmed <yosryahmed-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> Acked-by: Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> Acked-by: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org> Acked-by: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org> --- 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
next prev parent reply other threads:[~2023-03-30 19:18 UTC|newest] Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-03-30 19:17 [PATCH v3 0/8] memcg: avoid flushing stats atomically where possible Yosry Ahmed 2023-03-30 19:17 ` [PATCH v3 1/8] cgroup: rename cgroup_rstat_flush_"irqsafe" to "atomic" Yosry Ahmed 2023-03-30 19:17 ` Yosry Ahmed 2023-03-30 19:17 ` [PATCH v3 2/8] memcg: rename mem_cgroup_flush_stats_"delayed" to "ratelimited" Yosry Ahmed 2023-03-30 19:17 ` Yosry Ahmed [this message] 2023-03-30 19:17 ` [PATCH v3 3/8] memcg: do not flush stats in irq context Yosry Ahmed 2023-03-30 19:17 ` [PATCH v3 4/8] memcg: replace stats_flush_lock with an atomic Yosry Ahmed 2023-04-04 16:52 ` Michal Koutný 2023-04-04 16:52 ` Michal Koutný 2023-04-04 17:13 ` Shakeel Butt 2023-04-04 17:13 ` Shakeel Butt 2023-04-04 17:21 ` Shakeel Butt 2023-04-04 17:21 ` Shakeel Butt 2023-04-04 17:32 ` Michal Koutný 2023-03-30 19:17 ` [PATCH v3 5/8] memcg: sleep during flushing stats in safe contexts Yosry Ahmed 2023-03-30 19:30 ` Johannes Weiner 2023-04-04 15:09 ` Johannes Weiner 2023-03-30 19:17 ` [PATCH v3 6/8] workingset: memcg: sleep when flushing stats in workingset_refault() Yosry Ahmed 2023-04-04 16:53 ` Michal Koutný 2023-04-04 16:53 ` Michal Koutný 2023-04-04 18:09 ` Yosry Ahmed 2023-04-05 8:00 ` Michal Koutný 2023-04-05 8:00 ` Michal Koutný 2023-04-05 8:02 ` Yosry Ahmed 2023-04-05 8:02 ` Yosry Ahmed 2023-03-30 19:18 ` [PATCH v3 7/8] vmscan: memcg: sleep when flushing stats during reclaim Yosry Ahmed 2023-03-30 19:18 ` Yosry Ahmed 2023-03-30 19:18 ` [PATCH v3 8/8] memcg: do not modify rstat tree for zero updates Yosry Ahmed 2023-03-30 19:18 ` Yosry Ahmed 2023-04-04 16:53 ` Michal Koutný
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