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Thu, 23 Mar 2023 09:00:31 -0700 (PDT) Date: Thu, 23 Mar 2023 12:00:30 -0400 From: Johannes Weiner To: Yosry Ahmed Cc: Tejun Heo , Josef Bacik , Jens Axboe , Zefan Li , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Vasily Averin , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org Subject: Re: [RFC PATCH 6/7] workingset: memcg: sleep when flushing stats in workingset_refault() Message-ID: <20230323160030.GD739026@cmpxchg.org> References: <20230323040037.2389095-1-yosryahmed@google.com> <20230323040037.2389095-7-yosryahmed@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230323040037.2389095-7-yosryahmed@google.com> X-Rspamd-Queue-Id: A6823120027 X-Stat-Signature: jnnu5sgkj6h4xzd3er6sogiwkmbjfg98 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1679587232-969746 X-HE-Meta: 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 MOx2JY/l 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 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 Thu, Mar 23, 2023 at 04:00:36AM +0000, Yosry Ahmed wrote: > In workingset_refault(), we call mem_cgroup_flush_stats_delayed() to > flush stats within an RCU read section and with sleeping disallowed. > Move the call to mem_cgroup_flush_stats_delayed() above the RCU read > section and allow sleeping to avoid unnecessarily performing a lot of > work without sleeping. > > Signed-off-by: Yosry Ahmed > --- > > A lot of code paths call into workingset_refault(), so I am not > generally sure at all whether it's okay to sleep in all contexts or not. > Feedback here would be very helpful. > > --- > mm/workingset.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/mm/workingset.c b/mm/workingset.c > index 042eabbb43f6..410bc6684ea7 100644 > --- a/mm/workingset.c > +++ b/mm/workingset.c > @@ -406,6 +406,8 @@ void workingset_refault(struct folio *folio, void *shadow) > unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &workingset); > eviction <<= bucket_order; > > + /* Flush stats (and potentially sleep) before holding RCU read lock */ > + mem_cgroup_flush_stats_delayed(true); Btw, it might be a good time to rename this while you're in the area. delayed suggests this is using a delayed_work, but this is actually sometimes flushing directly from the callsite. What it's doing is ratelimited calls. A better name would be: mem_cgroup_flush_stats_ratelimited()