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s=arc-20220608; d=hostedemail.com; t=1765888496; a=rsa-sha256; cv=none; b=YW2MOr3FJnTULm4Nf7UJOa9ENZnI1rWQsYaV9IBF22bG+9dwB8GkziG3I3wsf2t8MfiJIj hXXL/Ik+eGd+Bto3G6mAZwLrFj/DfmAKcFQ22vrGPOnnGYw6bt0C8oYFyXnLNDi/6cjkKm oOiMnp88cLTVg9g/nYofsqe1ReafN9I= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=none; spf=pass (imf27.hostedemail.com: domain of chenridong@huaweicloud.com designates 45.249.212.51 as permitted sender) smtp.mailfrom=chenridong@huaweicloud.com; dmarc=none Received: from mail.maildlp.com (unknown [172.19.163.170]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4dVxFR1ppfzYQtkG for ; Tue, 16 Dec 2025 20:34:19 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id 708084056D for ; Tue, 16 Dec 2025 20:34:44 +0800 (CST) Received: from [10.67.111.176] (unknown [10.67.111.176]) by APP4 (Coremail) with SMTP id gCh0CgCHNvfhUUFpcimUAQ--.7655S2; Tue, 16 Dec 2025 20:34:42 +0800 (CST) Message-ID: <476fcde5-d54d-4b15-9870-844b3b8c700a@huaweicloud.com> Date: Tue, 16 Dec 2025 20:34:40 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH -next v3 2/2] memcg: remove mem_cgroup_size() To: =?UTF-8?Q?Michal_Koutn=C3=BD?= Cc: hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, akpm@linux-foundation.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, david@kernel.org, zhengqi.arch@bytedance.com, lorenzo.stoakes@oracle.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, lujialin4@huawei.com References: <20251211013019.2080004-1-chenridong@huaweicloud.com> <20251211013019.2080004-3-chenridong@huaweicloud.com> Content-Language: en-US From: Chen Ridong In-Reply-To: Content-Type: text/plain; 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Its semantics are unclear and >> inconsistent with other sites, which directly call page_counter_read for >> the same purpose. >> >> Remove this helper and get its usage via mem_cgroup_protection for >> clarity. Additionally, rename the local variable 'cgroup_size' to 'usage' >> to better reflect its meaning. >> >> No functional changes intended. >> >> Signed-off-by: Chen Ridong > > Why does mem_cgroup_calculate_protection "calculate" usage for its > callers? Couldn't you just the change source in > apply_proportional_protection()? > > Thanks, > Michal > I apologize for missing this message earlier. In my v2 patch, I was reading the usage directly: + unsigned long usage = page_counter_read(&memcg->memory); This works fine when CONFIG_MEMCG=y, but fails to compile when memory cgroups are disabled. To handle this, I initially added #ifdef CONFIG_MEMCG guards. Following Johannes's suggestion, I have now moved this logic into mem_cgroup_protection() to eliminate the #ifdef and keep the code cleaner. Discussion: https://lore.kernel.org/all/20251210163634.GB643576@cmpxchg.org/ >> @@ -2485,7 +2485,6 @@ static unsigned long apply_proportional_protection(struct mem_cgroup *memcg, >> * again by how much of the total memory used is under >> * hard protection. >> */ >> - unsigned long cgroup_size = mem_cgroup_size(memcg); > + unsigned long cgroup_size = page_counter_read(memcg); > >> unsigned long protection; >> >> /* memory.low scaling, make sure we retry before OOM */ >> @@ -2497,9 +2496,9 @@ static unsigned long apply_proportional_protection(struct mem_cgroup *memcg, >> } >> >> /* Avoid TOCTOU with earlier protection check */ >> - cgroup_size = max(cgroup_size, protection); >> + usage = max(usage, protection); >> >> - scan -= scan * protection / (cgroup_size + 1); >> + scan -= scan * protection / (usage + 1); >> >> /* >> * Minimally target SWAP_CLUSTER_MAX pages to keep -- Best regards, Ridong