From: Yosry Ahmed <yosryahmed@google.com>
To: Michal Hocko <mhocko@suse.com>
Cc: "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>,
"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>,
"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
Subject: Re: [PATCH v2 7/9] workingset: memcg: sleep when flushing stats in workingset_refault()
Date: Thu, 30 Mar 2023 00:42:36 -0700 [thread overview]
Message-ID: <CAJD7tkZLBs=A8m5u=9jGtMeD0ptOgtCTYUoh2r4Ex+fCkvwAXg@mail.gmail.com> (raw)
In-Reply-To: <ZCU8tjqzg8cDbobQ@dhcp22.suse.cz>
On Thu, Mar 30, 2023 at 12:39 AM Michal Hocko <mhocko@suse.com> wrote:
>
> On Tue 28-03-23 22:16:42, Yosry Ahmed wrote:
> > In workingset_refault(), we call
> > mem_cgroup_flush_stats_atomic_ratelimited() to flush stats within an
> > RCU read section and with sleeping disallowed. Move the call above
> > the RCU read section and allow sleeping to avoid unnecessarily
> > performing a lot of work without sleeping.
>
> Could you say few words why the flushing is done before counters are
> updated rather than after (the RCU section)?
It's not about the counters that are updated, it's about the counters
that we read. Stats readers do a flush first to read accurate stats.
We flush before a read, not after an update.
> --
> Michal Hocko
> SUSE Labs
next prev parent reply other threads:[~2023-03-30 7:43 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-28 22:16 [PATCH v2 0/9] memcg: make rstat flushing irq and sleep Yosry Ahmed
2023-03-28 22:16 ` [PATCH v2 1/9] cgroup: rename cgroup_rstat_flush_"irqsafe" to "atomic" Yosry Ahmed
2023-03-28 22:16 ` [PATCH v2 2/9] memcg: rename mem_cgroup_flush_stats_"delayed" to "ratelimited" Yosry Ahmed
2023-03-29 11:56 ` Michal Hocko
2023-03-28 22:16 ` [PATCH v2 3/9] memcg: do not flush stats in irq context Yosry Ahmed
2023-03-29 11:58 ` Michal Hocko
2023-03-28 22:16 ` [PATCH v2 4/9] cgroup: rstat: add WARN_ON_ONCE() if flushing outside task context Yosry Ahmed
2023-03-29 11:22 ` Michal Hocko
2023-03-29 18:41 ` Yosry Ahmed
2023-03-29 19:20 ` Shakeel Butt
2023-03-30 7:06 ` Michal Hocko
2023-03-30 7:13 ` Yosry Ahmed
2023-03-30 7:49 ` Michal Hocko
2023-03-30 8:06 ` Yosry Ahmed
2023-03-30 8:14 ` Michal Hocko
2023-03-30 8:19 ` Yosry Ahmed
2023-03-30 8:39 ` Michal Hocko
2023-03-30 8:53 ` Yosry Ahmed
2023-03-31 11:02 ` Michal Hocko
2023-03-31 19:03 ` Yosry Ahmed
2023-04-03 8:38 ` Michal Hocko
2023-04-03 20:39 ` Yosry Ahmed
2023-03-28 22:16 ` [PATCH v2 5/9] memcg: replace stats_flush_lock with an atomic Yosry Ahmed
2023-03-28 22:22 ` Shakeel Butt
2023-03-29 15:58 ` Michal Hocko
2023-03-29 18:45 ` Yosry Ahmed
2023-03-28 22:16 ` [PATCH v2 6/9] memcg: sleep during flushing stats in safe contexts Yosry Ahmed
2023-03-30 7:35 ` Michal Hocko
2023-03-28 22:16 ` [PATCH v2 7/9] workingset: memcg: sleep when flushing stats in workingset_refault() Yosry Ahmed
2023-03-30 7:39 ` Michal Hocko
2023-03-30 7:42 ` Yosry Ahmed [this message]
2023-03-30 7:50 ` Michal Hocko
2023-03-30 7:55 ` Yosry Ahmed
2023-03-28 22:16 ` [PATCH v2 8/9] vmscan: memcg: sleep when flushing stats during reclaim Yosry Ahmed
2023-03-30 7:40 ` Michal Hocko
2023-03-30 7:44 ` Yosry Ahmed
2023-03-30 7:52 ` Michal Hocko
2023-03-30 7:54 ` Yosry Ahmed
2023-03-28 22:16 ` [PATCH v2 9/9] memcg: do not modify rstat tree for zero updates Yosry Ahmed
2023-03-30 7:43 ` Michal Hocko
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