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h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=oXWrazzdj4fEldueS4rULJ5F/DAW9Te1RVNyHNBdkoXhUW9Wx3X6kYxQikIFgJnJL s0ZnPj+Ha+FnZCKm+LB+yErJsPvh/5MVORN17pUuGEfTB4nhK8XBXYrdWCkocGxKiu RVm0g7wPCbb5iDcsj4hjM/VQzx/i0RG7NYWEun1lUOJ8w+BBFt0As6Pqfw/+KOAtLX i6m6wQRMKxUZLxdxBw5jcihA15/9my3kZphYYEOprR0sRp4VmflVd0KUCsYqe12qcy 5gqcXAuaM2iEHQiin2LYU6Q/pjxqR6qfAu9dgz8RUW7Hakb2huEHBYGauzrizQGB/d yALJaa0qh581w== Received: by mail-pf1-f178.google.com with SMTP id d2e1a72fcca58-6c3363a2b93so2219090b3a.3 for ; Fri, 17 Nov 2023 10:27:56 -0800 (PST) X-Gm-Message-State: AOJu0YzX/7N7JMN3XRa0vKwQ45S2WSfy85Q9XwUUFkNZgiJkUiy2ZeDM Au6z6E3QeLQvPtQvMuz3pLjW5p8/9Gn5HDAH90LR2A== X-Google-Smtp-Source: AGHT+IFoONsJ5TfEjg90Ha4FkisHSprLoOsbnKOCvt55cyMLKRofW8yCafXcaCGInFvYbr5apUmtHKRD6VY5ZEM3NNg= X-Received: by 2002:a17:90b:1c83:b0:27d:b3d:5c33 with SMTP id oo3-20020a17090b1c8300b0027d0b3d5c33mr386546pjb.28.1700245675572; Fri, 17 Nov 2023 10:27:55 -0800 (PST) MIME-Version: 1.0 References: <20231116022411.2250072-1-yosryahmed@google.com> <20231116022411.2250072-2-yosryahmed@google.com> In-Reply-To: <20231116022411.2250072-2-yosryahmed@google.com> From: Chris Li Date: Fri, 17 Nov 2023 10:27:44 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 1/5] mm: memcg: change flush_next_time to flush_last_time To: Yosry Ahmed Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Ivan Babrou , Tejun Heo , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Waiman Long , kernel-team@cloudflare.com, Wei Xu , Greg Thelen , Domenico Cerasuolo , linux-mm , cgroups@vger.kernel.org, LKML Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 33F96C0011 X-Stat-Signature: 34m6j394hpzsioqxb9x817nw3sydzmhh X-HE-Tag: 1700245678-912532 X-HE-Meta: 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 T+L4cyrC 9YHru581ejUjCc2881XTPVcS5mkTbLRDLQa89bOcOoT5jJvQnT1PfCiw0BZSIY3qpW1jfQLyU8lIpzX7hBImfK6ERT0zlfYdRkLWa4NpaQE4ZlXNK9FDzOMadI9BLvlxIBFNtB2NZ4FbPTIZ07GhuKGtpMGBnR8PUkgZxHDfrwfALqmadp6j9h5cf2aDFI9Puk06yllJTmQ+EfvcDMm15lQ/qyFHDweTVd1PaNeftfebp+6WiWlojggGYhW9kZ1DNHPWO7NRrn8v6f1PGQAXUe7X4a35lcaq2KnFys7P94qgUa0H9yG8WEMzIlWYxGahH5NkNp2c1AmtwvYhAQ2XhmRgYA49kba6kmXY03OyHIlqQUXOMWxRZ8pmpYw== 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: List-Subscribe: List-Unsubscribe: Hi Yosry, Acked-by: Chris Li (Google) Chris On Wed, Nov 15, 2023 at 6:24=E2=80=AFPM Yosry Ahmed = wrote: > > flush_next_time is an inaccurate name. It's not the next time that > periodic flushing will happen, it's rather the next time that > ratelimited flushing can happen if the periodic flusher is late. > > Simplify its semantics by just storing the timestamp of the last flush > instead, flush_last_time. Move the 2*FLUSH_TIME addition to > mem_cgroup_flush_stats_ratelimited(), and add a comment explaining it. > This way, all the ratelimiting semantics live in one place. > > No functional change intended. > > Signed-off-by: Yosry Ahmed > Tested-by: Domenico Cerasuolo > --- > mm/memcontrol.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 774bd6e21e278..18931d82f108f 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -593,7 +593,7 @@ static DECLARE_DEFERRABLE_WORK(stats_flush_dwork, flu= sh_memcg_stats_dwork); > static DEFINE_PER_CPU(unsigned int, stats_updates); > static atomic_t stats_flush_ongoing =3D ATOMIC_INIT(0); > static atomic_t stats_flush_threshold =3D ATOMIC_INIT(0); > -static u64 flush_next_time; > +static u64 flush_last_time; > > #define FLUSH_TIME (2UL*HZ) > > @@ -653,7 +653,7 @@ static void do_flush_stats(void) > atomic_xchg(&stats_flush_ongoing, 1)) > return; > > - WRITE_ONCE(flush_next_time, jiffies_64 + 2*FLUSH_TIME); > + WRITE_ONCE(flush_last_time, jiffies_64); > > cgroup_rstat_flush(root_mem_cgroup->css.cgroup); > > @@ -669,7 +669,8 @@ void mem_cgroup_flush_stats(void) > > void mem_cgroup_flush_stats_ratelimited(void) > { > - if (time_after64(jiffies_64, READ_ONCE(flush_next_time))) > + /* Only flush if the periodic flusher is one full cycle late */ > + if (time_after64(jiffies_64, READ_ONCE(flush_last_time) + 2*FLUSH= _TIME)) > mem_cgroup_flush_stats(); > } > > -- > 2.43.0.rc0.421.g78406f8d94-goog > >