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From: Roman Gushchin To: Shakeel Butt Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Muchun Song , Steven Rostedt , JP Kobryn , Yosry Ahmed , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: Re: [PATCH] memcg: add tracing for memcg stat updates Message-ID: References: <20241010003550.3695245-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241010003550.3695245-1-shakeel.butt@linux.dev> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Stat-Signature: ny5fje8jt8ztfzqndjhzstfhm61jipii X-Rspamd-Queue-Id: EE45B1C000C X-Rspamd-Server: rspam02 X-HE-Tag: 1728521202-77542 X-HE-Meta: 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 NzBuJiiN VoCfq68FgD9xo7xPDj8p5Oz/TkgiUloXQPiWMUMqbtrnlzANY67QDI3QE8CXsLqpf3C8K3GyqQTlb7/7Xh+SMm41ku/gRqyIlYFe7tFre8R6Ow735mOXBwkEGMnzvKcn2E8T932nxioTix8wzYAJSQUWNNUKTZlJGYKWAQKjFeqAEZ98mAd9WCUvY3w== 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: On Wed, Oct 09, 2024 at 05:35:50PM -0700, Shakeel Butt wrote: > The memcg stats are maintained in rstat infrastructure which provides > very fast updates side and reasonable read side. However memcg added > plethora of stats and made the read side, which is cgroup rstat flush, > very slow. To solve that, threshold was added in the memcg stats read > side i.e. no need to flush the stats if updates are within the > threshold. > > This threshold based improvement worked for sometime but more stats were > added to memcg and also the read codepath was getting triggered in the > performance sensitive paths which made threshold based ratelimiting > ineffective. We need more visibility into the hot and cold stats i.e. > stats with a lot of updates. Let's add trace to get that visibility. > > Signed-off-by: Shakeel Butt Acked-by: Roman Gushchin Thanks!