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h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=SOC1y4YdF+TE8yz5hNlXQ4JYtHhx8XCf13Ewvl3BZpJHD4HFntapHnOun+DQ1YiU6 sRBl0hbkAjT6GAtlyFdkJJFbBPUMs0ZNO4G94SE7JQRcmzFdh7Nx3E3bHdTfE5NZRf eKDVMk038Ga0vDeZjdqbhQ2aVJ06JSxxuXgrJD98DVaGxArBW9tx40bADmb9Xqzl63 HgX1XbA1e5oa9k5lcIEaEWS8uiE68t1s3i5BM+90h9MfNUy91SPs+yCUMU0WqJvGaw L26RWxif6II6ufNLGtCKuoT0XuQ6IXOYK9YUZwhjueZi8UgjGqwJHRfZuSRqOud4kO vRpBHAklN3S3Q== Received: by mail-ed1-f45.google.com with SMTP id 4fb4d7f45d1cf-66c3635d758so88613a12.3 for ; Mon, 30 Mar 2026 12:02:49 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCX7knalo8xjK6GwflL+QEol2nbqXu32v3rYVgsTZFEstvrlxMfOOEoCU1y2eicAH5fopBpiGGAZmw==@kvack.org X-Gm-Message-State: AOJu0Yzi0ywunEJXPHtxu7qOs1ptBxg08538tjqHoz9+qRI2UAPRapVA uZyKdP2B2gxmY4hunzVOLCohQmKyQnBOjrub/uaYLb2d2DQHnMnZhi4OVAnaFDb6ns7GOqA38ez eiHeHu76pJSR1mzHyEiAZOltRyxumQZc= X-Received: by 2002:a17:907:cb13:b0:b96:e3db:9e04 with SMTP id a640c23a62f3a-b9b5094edf8mr570685066b.53.1774897368210; Mon, 30 Mar 2026 12:02:48 -0700 (PDT) MIME-Version: 1.0 References: <20260330185947.2427740-1-joshua.hahnjy@gmail.com> In-Reply-To: <20260330185947.2427740-1-joshua.hahnjy@gmail.com> From: Yosry Ahmed Date: Mon, 30 Mar 2026 12:02:35 -0700 X-Gmail-Original-Message-ID: X-Gm-Features: AQROBzD5Q4JVONjgLXuHQnh-7_hxGvOUjkM2GvDUWYmix-4crTfbUhCwaZZfCG4 Message-ID: Subject: Re: [PATCH] mm/percpu, memcontrol: Per-memcg-lruvec percpu accounting To: Joshua Hahn Cc: Michal Hocko , Johannes Weiner , Andrew Morton , Roman Gushchin , Shakeel Butt , Muchun Song , David Hildenbrand , Lorenzo Stoakes , Vlastimil Babka , Dennis Zhou , Tejun Heo , Christoph Lameter , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 9430480005 X-Stat-Signature: nwsshmkknbx8dhi3udk8pwaag7khuabs X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1774897370-672782 X-HE-Meta: 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 lC4TGMhB vWx0uYTQVBAtyD7Alhx3sadT9RjaQ7h6exMjaxcL2Dw+u6Mdk2fSV06bYIol57fFX2MpVNIp+4AEjS5ylHM4+gNBAe8HApAedX55q4QoLvccaIjQIv9MFzPCd0FgTp7wpYgavwrD/xrHvRfMPo1AmpI+KbFudbjaSG60Gknrlv6CzAratVVcmXVSOcli3djCycd3MHMSEVC0t14m3VkLzgVdj1ulkva06h5W+8NZLH0gZoEz5oTyEoG4Vw4bpnwv5v+mGjU6prmQt5MRCH13bGJ4P1L+XWdq1GrglwTK/qYRAhwyfo/WHSPMk3/f8Lop6jws6 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > > You should probably also speak to extra memory overhead to move all > > these stats from per-memcg to per-lruvec. > > Hello Yosry, > > Thank you for your feedback! > > Here are the things that I cna see from my end: > - NR_PERCPU_B adds a byte per-node, per-cpu. I think this is manageable. > - lruvec_stats_percpu grows by 1 long in 2 arrays (state, state_prev) since > NR_MEMCG_NODE_STAT_ITEMS grows by 1 from ~30. This is +16 bytes per > cgroup x node x CPU. Even still, I'm not sure this is too concerning, > on a host with 300 CPUs across 2 nodes with 100 cgroups (theoretical) > we would see a 16 * 300 * 2 * 100 = 937 kB change, less than a mB (and > I think this would be considered a big machine). > > What do you think? Do these numbers look acceptable? Oh I wasn't trying to say whether this is acceptable or not, just that this is a relevant context that should be included to help people see the tradeoff clearly and make a decision. > > Thanks again for your insights, I hope you have a great day : -) > Joshua >