diff mbox series

[v1,9/9] memcg: do not modify rstat tree for zero updates

Message ID	20230328061638.203420-10-yosryahmed@google.com
State	New
Headers	Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Date: Tue, 28 Mar 2023 06:16:38 +0000 In-Reply-To: <20230328061638.203420-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230328061638.203420-1-yosryahmed@google.com> Message-ID: <20230328061638.203420-10-yosryahmed@google.com> Subject: [PATCH v1 9/9] memcg: do not modify rstat tree for zero updates 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>, " =?utf-8?q?Michal_Koutn=C3=BD?= " <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> Content-Type: text/plain; charset="UTF-8" Precedence: bulk
Series	memcg: make rstat flushing irq and sleep friendly \| [v1,0/9] memcg: make rstat flushing irq and sleep friendly [v1,1/9] cgroup: rename cgroup_rstat_flush_"irqsafe" to "atomic" [v1,2/9] memcg: rename mem_cgroup_flush_stats_"delayed" to "ratelimited" [v1,3/9] memcg: do not flush stats in irq context [v1,4/9] cgroup: rstat: add WARN_ON_ONCE() if flushing outside task context [v1,5/9] memcg: replace stats_flush_lock with an atomic [v1,6/9] memcg: sleep during flushing stats in safe contexts [v1,7/9] workingset: memcg: sleep when flushing stats in workingset_refault() [v1,8/9] vmscan: memcg: sleep when flushing stats during reclaim [v1,9/9] memcg: do not modify rstat tree for zero updates

Commit Message

Yosry Ahmed March 28, 2023, 6:16 a.m. UTC

  In some situations, we may end up calling memcg_rstat_updated() with a
value of 0, which means the stat was not actually updated. An example is
if we fail to reclaim any pages in shrink_folio_list().

Do not add the cgroup to the rstat updated tree in this case, to avoid
unnecessarily flushing it.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
---
 mm/memcontrol.c | 3 +++
 1 file changed, 3 insertions(+)

Comments

Shakeel Butt March 28, 2023, 3:20 p.m. UTC | #1

On Mon, Mar 27, 2023 at 11:17 PM Yosry Ahmed <yosryahmed@google.com> wrote:
>
> In some situations, we may end up calling memcg_rstat_updated() with a
> value of 0, which means the stat was not actually updated. An example is
> if we fail to reclaim any pages in shrink_folio_list().
>
> Do not add the cgroup to the rstat updated tree in this case, to avoid
> unnecessarily flushing it.
>
> Signed-off-by: Yosry Ahmed <yosryahmed@google.com>

Acked-by: Shakeel Butt <shakeelb@google.com>

Johannes Weiner March 28, 2023, 6:50 p.m. UTC | #2

On Tue, Mar 28, 2023 at 06:16:38AM +0000, Yosry Ahmed wrote:
> In some situations, we may end up calling memcg_rstat_updated() with a
> value of 0, which means the stat was not actually updated. An example is
> if we fail to reclaim any pages in shrink_folio_list().
> 
> Do not add the cgroup to the rstat updated tree in this case, to avoid
> unnecessarily flushing it.
> 
> Signed-off-by: Yosry Ahmed <yosryahmed@google.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

diff mbox series

Patch

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0c0e74188e90..828e670e721a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -618,6 +618,9 @@  static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val)
 {
 	unsigned int x;
 
+	if (!val)
+		return;
+
 	cgroup_rstat_updated(memcg->css.cgroup, smp_processor_id());
 
 	x = __this_cpu_add_return(stats_updates, abs(val));