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Tue, 28 Mar 2023 12:29:49 -0700 (PDT) MIME-Version: 1.0 References: <20230328061638.203420-1-yosryahmed@google.com> <20230328061638.203420-9-yosryahmed@google.com> In-Reply-To: From: Shakeel Butt Date: Tue, 28 Mar 2023 12:29:38 -0700 Message-ID: Subject: Re: [PATCH v1 8/9] vmscan: memcg: sleep when flushing stats during reclaim To: Yosry Ahmed Cc: Tejun Heo , Josef Bacik , Jens Axboe , Zefan Li , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Andrew Morton , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Vasily Averin , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: EC04720014 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: z6omjgpe3nmsqx6qc34iae3pfj8iwfyn X-HE-Tag: 1680031789-495432 X-HE-Meta: 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 Q+YY15bG aUMG85yOuiUK9RojZU7XU248WaksaZ2HckGSq0CF4vEr28myPgkpubiW9Vype246F9SXcrPkD8BI5UpN21gT1DeDyDnExeODQTPgzG+MU36wICzCZETmroz9DZI5qcG7c4JG2yAj18luOUQE2tE9ub+Umi0rZu1MA+E6n/nJUiYj16ouvOQoRnWOEOD6oXACUQ1OGojrlHyJ1rz3Vc8G3RQWS36X2+wdOcai34Lgjp9bt1+FP9eHgaAwxsgvi6t+lHJXBdPGpoamsH/Tcpo49s27o8/GV1d5kq+LeNuO9w0V/guBXf31RwKLKHw== 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, Mar 28, 2023 at 12:02=E2=80=AFPM Yosry Ahmed wrote: > > On Tue, Mar 28, 2023 at 8:19=E2=80=AFAM Shakeel Butt wrote: > > > > On Mon, Mar 27, 2023 at 11:16=E2=80=AFPM Yosry Ahmed wrote: > > > > > > Memory reclaim is a sleepable context. Allow sleeping when flushing > > > memcg stats to avoid unnecessarily performing a lot of work without > > > sleeping. This can slow down reclaim code if flushing stats is taking > > > too long, but there is already multiple cond_resched()'s in reclaim > > > code. > > > > > > Signed-off-by: Yosry Ahmed > > > > Acked-by: Shakeel Butt > > > > > --- > > > mm/vmscan.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > > index a9511ccb936f..9c1c5e8b24b8 100644 > > > --- a/mm/vmscan.c > > > +++ b/mm/vmscan.c > > > @@ -2845,7 +2845,7 @@ static void prepare_scan_count(pg_data_t *pgdat= , struct scan_control *sc) > > > * Flush the memory cgroup stats, so that we read accurate pe= r-memcg > > > * lruvec stats for heuristics. > > > */ > > > - mem_cgroup_flush_stats_atomic(); > > > + mem_cgroup_flush_stats(); > > > > I wonder if we should just replace this with > > mem_cgroup_flush_stats_ratelimited(). > > Thanks for taking a look! > > I was hesitant about doing this because the flush call is inside the > retry loop, and it seems like we want to get fresh stats on each > retry. It seems very likely that we end up not flushing between > retries with mem_cgroup_flush_stats_ratelimited(). > > Maybe change it if we observe problems with non-atomic flushing? Yeah, let's leave it for the future if we see the issue.