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Thu, 12 Oct 2023 16:29:26 -0700 (PDT) MIME-Version: 1.0 References: <20231010032117.1577496-1-yosryahmed@google.com> <20231010032117.1577496-4-yosryahmed@google.com> <20231011003646.dt5rlqmnq6ybrlnd@google.com> <20231012132946.GA470544@cmpxchg.org> In-Reply-To: <20231012132946.GA470544@cmpxchg.org> From: Yosry Ahmed Date: Thu, 12 Oct 2023 16:28:49 -0700 Message-ID: Subject: Re: [PATCH v2 3/5] mm: memcg: make stats flushing threshold per-memcg To: Johannes Weiner Cc: Shakeel Butt , Andrew Morton , Michal Hocko , Roman Gushchin , Muchun Song , Ivan Babrou , Tejun Heo , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Waiman Long , kernel-team@cloudflare.com, Wei Xu , Greg Thelen , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: B1BA916000E X-Stat-Signature: trhyo4x1yuqieuie9gyhck3ab8bo88kt X-HE-Tag: 1697153368-280240 X-HE-Meta: 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 9TvBcpPz nWAHZ+DZMPXftl+Ljwao/U/qRf7DN/y4LxC3Yhsu3xCZPdnvA3Rxo0pD2VMpBek3WAYElLQZULj+DVg+b+ftUXpSVNilUYzYaZFFILYa8cMtNQG3QqfaRKkXWVVKnbjg2mFP+yAoPc7/UkNxFI3ztj8s8hdNG7a4elxFB6yUDMLoSoHuYM9bdz4YVrjYz7C+QZW0qVHhDDfwQHBAgxODn7qnQs7AhUgNVU2TsGScm26W9Og4tGZOvNBU9sui9lFQzZ3TctAujqfxQ9QP9FBtRMrA4Fuk5SuvM790Kn9MadQtvVy5d8m7Duzz9JhV7XGbYtxC3g5GyFYc0gN1cUuxD4p9TlA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000881, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: [..] > > > > > > Using next-20231009 and a similar 44 core machine with hyperthreading > > > disabled, I ran 22 instances of netperf in parallel and got the > > > following numbers from averaging 20 runs: > > > > > > Base: 33076.5 mbps > > > Patched: 31410.1 mbps > > > > > > That's about 5% diff. I guess the number of iterations helps reduce > > > the noise? I am not sure. > > > > > > Please also keep in mind that in this case all netperf instances are > > > in the same cgroup and at a 4-level depth. I imagine in a practical > > > setup processes would be a little more spread out, which means less > > > common ancestors, so less contended atomic operations. > > > > > > (Resending the reply as I messed up the last one, was not in plain text) > > > > I was curious, so I ran the same testing in a cgroup 2 levels deep > > (i.e /sys/fs/cgroup/a/b), which is a much more common setup in my > > experience. Here are the numbers: > > > > Base: 40198.0 mbps > > Patched: 38629.7 mbps > > > > The regression is reduced to ~3.9%. > > > > What's more interesting is that going from a level 2 cgroup to a level > > 4 cgroup is already a big hit with or without this patch: > > > > Base: 40198.0 -> 33076.5 mbps (~17.7% regression) > > Patched: 38629.7 -> 31410.1 (~18.7% regression) > > > > So going from level 2 to 4 is already a significant regression for > > other reasons (e.g. hierarchical charging). This patch only makes it > > marginally worse. This puts the numbers more into perspective imo than > > comparing values at level 4. What do you think? > > I think it's reasonable. > > Especially comparing to how many cachelines we used to touch on the > write side when all flushing happened there. This looks like a good > trade-off to me. Thanks. Still wanting to figure out if this patch is what you suggested in our previous discussion [1], to add a Suggested-by if appropriate :) [1]https://lore.kernel.org/lkml/20230913153758.GB45543@cmpxchg.org/