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c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1765356141; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=HeryyzZzLp65h/NZGcvmK52pZNFHK5D9WdENI+2hwvk=; b=sw/zKRNERixadFVrChvg+31CINhqVYhVwXgTFB011HXFXUh7w2X5Tp6DcUB4YZWA+WPru3 w1ojER9MSDVxfNWXPahxUXbkZe4Ibev0pPVN1n+1QTKjgXXFwbjp7qrmjbsdYFAjfoyuGF +XmeZoswu856y9qoOVdSzeHw3ylwiWw= Received: from mail.maildlp.com (unknown [172.19.93.142]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4dR8MD1JvyzKHMn4 for ; Wed, 10 Dec 2025 16:41:12 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.75]) by mail.maildlp.com (Postfix) with ESMTP id EF5B91A084D for ; Wed, 10 Dec 2025 16:42:11 +0800 (CST) Received: from [10.67.111.176] (unknown [10.67.111.176]) by APP2 (Coremail) with SMTP id Syh0CgBXOFJiMjlpL9n3BA--.10261S2; Wed, 10 Dec 2025 16:42:11 +0800 (CST) Message-ID: <48f734fa-531a-4b3f-9c96-02dd342d41d2@huaweicloud.com> Date: Wed, 10 Dec 2025 16:42:09 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH -next v2 2/2] memcg: remove mem_cgroup_size() To: Michal Hocko Cc: hannes@cmpxchg.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: <20251210071142.2043478-1-chenridong@huaweicloud.com> <20251210071142.2043478-3-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 replace its usage with page_counter_read for >> clarity. Additionally, rename the local variable 'cgroup_size' to 'usage' >> to better reflect its meaning. >> >> This change is safe because page_counter_read() is only called when memcg >> is enabled in the apply_proportional_protection. >> >> No functional changes intended. > > I would prefer to keep the code as is. > I find the mem_cgroup_size() function name misleading—it suggests counting the number of memory cgroups, but it actually returns the current memory usage. When looking for a clearer alternative, I found mem_cgroup_usage(), which is only called by v1. This raised the question of whether mem_cgroup_size() is truly necessary. Moreover, I noticed other code locations simply call page_counter_read() directly to obtain current usage. > Btw. > [...] >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index 670fe9fae5ba..fe48d0376e7c 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -2451,6 +2451,7 @@ static inline void calculate_pressure_balance(struct scan_control *sc, >> static unsigned long apply_proportional_protection(struct mem_cgroup *memcg, >> struct scan_control *sc, unsigned long scan) >> { >> +#ifdef CONFIG_MEMCG >> unsigned long min, low; >> >> mem_cgroup_protection(sc->target_mem_cgroup, memcg, &min, &low); > [...] >> @@ -2508,6 +2509,7 @@ static unsigned long apply_proportional_protection(struct mem_cgroup *memcg, >> */ >> scan = max(scan, SWAP_CLUSTER_MAX); >> } >> +#endif >> return scan; >> } > > This returns a random garbage for !CONFIG_MEMCG, doesn't it? > -- Best regards, Ridong