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b=hObn2qOaq0A3X+0I/izOXtHdCNfRASbw87T3QgCGYi/yv0rN3eSrFnWlHLyezIN5IwoEcadQzCazc6zLqKLCAChfDQWtc7zcupV36M6SD9i9XAHWHzFGFyFT0PuKhz1TCKJZKb9Q3rnGA1C9ZDxtYdilA/PtlNmrvgt0M1uS/0I= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R121e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033032089153;MF=qinyuntan@linux.alibaba.com;NM=1;PH=DS;RN=20;SR=0;TI=SMTPD_---0XAgyQpm_1789026012; Received: from 30.178.84.157(mailfrom:qinyuntan@linux.alibaba.com fp:SMTPD_---0XAgyQpm_1789026012 cluster:ay36) by smtp.aliyun-inc.com; Thu, 10 Sep 2026 15:40:17 +0800 Message-ID: Date: Thu, 10 Sep 2026 15:40:12 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] mm: memcontrol: drop kmemcg_id and use the memcg ID for list_lru indexing To: Johannes Weiner Cc: Andrew Morton , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , =?UTF-8?Q?Michal_Koutn=C3=BD?= , David Hildenbrand , Zi Yan , Baolin Wang , Usama Arif , Dave Chinner , Qi Zheng , Yosry Ahmed , Nhat Pham , Chengming Zhou , Xunlei Pang , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260907110111.2286932-1-qinyuntan@linux.alibaba.com> <20260907110111.2286932-2-qinyuntan@linux.alibaba.com> From: Qinyun Tan In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 93C8E180009 X-Rspam-User: X-Stat-Signature: kh6ynyds6jtr6rpznag7g5416rsrkdps X-HE-Tag: 1789026022-804106 X-HE-Meta: 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 VD6Il/P5 oweSqm+4/ywLZYF54e37+5LjpaKqafLFybrmz52BcmV6/Mnvw06/Bt2j7BZWlxlpvdKuryyVBuwltdCxK8e0meMLKgCHHXBj8lYQY5KkBlazFLlmnQu0cgOj4bLNCLyhdrAVv/JtOYWdOTZe7EZ8mfPvMcBQzmIPqO5jWKd5nGn6uo9bZozeOx+1TIOPl85Az2zkLqgbyhY2/TS7UoHQ0W7mzywo+BUfcFfaOVFBRNZeAJXMTG8jXUCXx3KUEiDrhMwTOsKWHHHa/kcd3EDkYAQVD3pLgaoCalg6StQkQIaVo72TC4NRws0u9uXLfrkKqw/U4Gb3XJhQSgqoQMSeSXOffc6B+JJQRxPGA0gHJT6GGkU4= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/10/26 2:21 AM, Johannes Weiner wrote: > On Mon, Sep 07, 2026 at 07:01:08PM +0800, Qinyun Tan wrote: > > This is a private ID with lifetime only guaranteed for online > groups. Reparenting happens right before it dies at offlining right > now, but this is not a great dependency to have. > > Use mem_cgroup_id() instead and just get rid of that helper. > Hi Johannes, Thanks for the review. Right, the copy of the private ID carried exactly that ordering dependency, and the cgroup ID removes it cleanly. mem_cgroup_id() it is. > Both of these functions do very little now and the asymmetry you're > adding on the mem_cgroup_kmem_disabled() check looks odd. Please just > inline them into mem_cgroup_css_online()/offline(): > > onlining: > if (!mem_cgroup_kmem_disabled() && likely(!mem_cgroup_is_root())) > static_branch_enable(&memcg_kmem_online_key); > > offlining: > memcg_reparent_list_lrus(memcg, parent); > > The root check is unnecessary because roots are not destroyed. But if > you'd rather not make that change here, keep the root check, and leave > its removal to a separate cleanup patch, that's fine too. > That makes sense. I'll send a v3 with these changes. Thanks again, Qinyun Tan