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bh=TvSV5fFGuEOFjUYyyYheVzehmeCjrTbwB5BCRB7nlmE=; b=LIArtXHabAx8zC14+MsCOdUiodNI8BJeAMl0xV48vPjk86z61XQQR//SnbsNqQwQ3muu9V wkka+0M/kTLweMEC0tZcqxeTaRpe2UzW3zI+gxh/HEE0ujhT8xZZyi8B0frjHVMhNZ7SpN up7wTOHbt09wphDQNj0d8m9+oNDrF90= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=none; spf=pass (imf30.hostedemail.com: domain of chenridong@huaweicloud.com designates 45.249.212.56 as permitted sender) smtp.mailfrom=chenridong@huaweicloud.com; dmarc=none Received: from mail.maildlp.com (unknown [172.19.163.216]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4dPmKT5DVrzKHLwf for ; Mon, 8 Dec 2025 10:34:53 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id 1B5631A191F for ; Mon, 8 Dec 2025 10:35:50 +0800 (CST) Received: from [10.67.111.176] (unknown [10.67.111.176]) by APP1 (Coremail) with SMTP id cCh0CgB3sX2EOTZpaUznAw--.9363S2; Mon, 08 Dec 2025 10:35:49 +0800 (CST) Message-ID: <14b2584b-3ac7-4358-9d81-40ca32683e4f@huaweicloud.com> Date: Mon, 8 Dec 2025 10:35:48 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH -next 1/2] mm/mglru: use mem_cgroup_iter for global reclaim To: zhongjinji , hannes@cmpxchg.org Cc: Liam.Howlett@oracle.com, akpm@linux-foundation.org, axelrasmussen@google.com, cgroups@vger.kernel.org, chenridong@huawei.com, corbet@lwn.net, david@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, lujialin4@huawei.com, mhocko@suse.com, muchun.song@linux.dev, roman.gushchin@linux.dev, rppt@kernel.org, shakeel.butt@linux.dev, surenb@google.com, vbabka@suse.cz, weixugc@google.com, yuanchu@google.com, yuzhao@google.com, zhengqi.arch@bytedance.com References: <20251204183437.GB481418@cmpxchg.org> <20251205025727.8324-1-zhongjinji@honor.com> Content-Language: en-US From: Chen Ridong In-Reply-To: <20251205025727.8324-1-zhongjinji@honor.com> Content-Type: text/plain; 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However, its implementation complexity has led to performance >> regressions when dealing with a large number of memory cgroups [1]. >> >> As suggested by Johannes [1], this patch adopts mem_cgroup_iter with >> cookie-based iteration for global reclaim, aligning with the approach >> already used in shrink_node_memcgs. This simplification removes the >> dedicated memcg LRU tracking while maintaining the core functionality. >> >> It performed a stress test based on Zhao Yu's methodology [2] on a >> 1 TB, 4-node NUMA system. The results are summarized below: >> >> memcg LRU memcg iter >> stddev(pgsteal) / mean(pgsteal) 91.2% 75.7% >> sum(pgsteal) / sum(requested) 216.4% 230.5% > > Are there more data available? For example, the load of kswapd or the refault values. > > I am concerned about these two data points because Yu Zhao's implementation controls > the fairness of aging through memcg gen (get_memcg_gen). This helps reduce excessive > aging for certain cgroups, which is beneficial for kswapd's power consumption. > > At the same time, pages that age earlier can be considered colder pages (in the entire system), > so reclaiming them should also help with the refault values. > I re-ran the test and observed a 3.2% increase in refaults. Is this enough for what you were concerned about? The complete data set is offered in my earlier email: https://lore.kernel.org/all/e657d5ac-6f92-4dbb-bf32-76084988d024@huaweicloud.com/ >> The new implementation demonstrates a significant improvement in >> fairness, reducing the standard deviation relative to the mean by >> 15.5 percentage points. While the reclaim accuracy shows a slight >> increase in overscan (from 85086871 to 90633890, 6.5%). >> >> The primary benefits of this change are: >> 1. Simplified codebase by removing custom memcg LRU infrastructure >> 2. Improved fairness in memory reclaim across multiple cgroups >> 3. Better performance when creating many memory cgroups >> >> [1] https://lore.kernel.org/r/20251126171513.GC135004@cmpxchg.org >> [2] https://lore.kernel.org/r/20221222041905.2431096-7-yuzhao@google.com >> Signed-off-by: Chen Ridong -- Best regards, Ridong