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b=v9gf1qnug911Bfd6CyT7PlmnqESXvi3VKOKiXhnMx1Ddu23Tde+q6DF6ACEr4O3Z2DmaF5c70eFEDqvDmhpdDRSAKQDbZ+xy9IkEG2q0UsDlxvJ4v0d1Y5K6v+5u+nvGn+OauX+HgQwXRFh+pFUSOBIHPOrGVg2KHn5B85PqbE4= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037026112;MF=qinyuntan@linux.alibaba.com;NM=1;PH=DS;RN=20;SR=0;TI=SMTPD_---0XAgyScL_1789026417; Received: from 30.178.84.157(mailfrom:qinyuntan@linux.alibaba.com fp:SMTPD_---0XAgyScL_1789026417 cluster:ay36) by smtp.aliyun-inc.com; Thu, 10 Sep 2026 15:46:58 +0800 Message-ID: Date: Thu, 10 Sep 2026 15:46:56 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/4] mm: thp: restore SHRINKER_NONSLAB on the deferred split shrinker 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> <20260907110111.2286932-4-qinyuntan@linux.alibaba.com> From: Qinyun Tan In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 3229540003 X-Stat-Signature: t19bbwe8apwh97x4jpm57nh841cr5qba X-HE-Tag: 1789026422-944748 X-HE-Meta: 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 XFEU1RsR 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Johannes, On 9/10/26 2:28 AM, Johannes Weiner wrote: > On Mon, Sep 07, 2026 at 07:01:10PM +0800, Qinyun Tan wrote: >> On a system booted with cgroup.memory=nokmem, the deferred split >> shrinker is quietly demoted to a non-memcg-aware one. As a result, >> partially unmapped THPs are only split under global reclaim; memcg >> (limit-induced) reclaim never splits them, so a cgroup under memory >> pressure keeps its underused THPs intact. >> >> This is a regression from commit fafaeceb89a5 ("mm: switch deferred >> split shrinker to list_lru"), which re-registered the shrinker without >> SHRINKER_NONSLAB. The shrinker had carried this flag since commit >> 0a432dcbeb32 ("mm: shrinker: make shrinker not depend on memcg kmem") >> precisely so it would keep working with kmem accounting disabled. >> Without the flag, shrinker_memcg_alloc() fails with -ENOSYS under >> nokmem and the shrinker loses its memcg awareness. > > Here is the reason why it was dropped: > https://lore.kernel.org/all/ah9PGv12mqai84ES@cmpxchg.org/ > > After your patch to make list_lru expand for NONSLAB shrinkers, it can > be restored. > Thanks for the pointer. I'll update the commit message in v3 and reference that thread. >> This was noticed by Michal during review of the patch "mm/list_lru: >> don't copy stale shrinker id from non-memcg-aware shrinkers" [1]. >> >> Restore the flag. >> >> [1] https://lore.kernel.org/lkml/697713c4-0857-485b-aba7-c74f37a3c8b4@linux.alibaba.com/ >> >> Fixes: fafaeceb89a5 ("mm: switch deferred split shrinker to list_lru") >> Suggested-by: Michal Koutný >> Signed-off-by: Qinyun Tan >> Acked-by: Zi Yan >> Acked-by: David Hildenbrand (Arm) >> Acked-by: Usama Arif >> Reviewed-by: Baolin Wang > > Reviewed-by: Johannes Weiner Thanks again, Qinyun Tan