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Received: from banye.tbsite.net(mailfrom:qinyuntan@linux.alibaba.com fp:SMTPD_---0XATsw.3_1788778878 cluster:ay36) by smtp.aliyun-inc.com; Mon, 07 Sep 2026 19:01:19 +0800 From: Qinyun Tan To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , =?UTF-8?q?Michal=20Koutn=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, Qinyun Tan Subject: [PATCH v2 3/4] mm: thp: restore SHRINKER_NONSLAB on the deferred split shrinker Date: Mon, 7 Sep 2026 19:01:10 +0800 Message-ID: <20260907110111.2286932-4-qinyuntan@linux.alibaba.com> X-Mailer: git-send-email 2.43.7 In-Reply-To: <20260907110111.2286932-1-qinyuntan@linux.alibaba.com> References: <20260907110111.2286932-1-qinyuntan@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: 6dhtmjyx5hsknyhzhyzga1q77ancx6wh X-Rspamd-Queue-Id: 9CEFAA0003 X-Rspamd-Server: rspam06 X-HE-Tag: 1788778883-250207 X-HE-Meta: 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 1UuOFDzG j6V6kuh5vJJFkAQp2j7qVLZwZrJd9zb6Ypii2krt7tBPsPAArT4OLJp6VHoHbL1BxEyJhQH57y9Tuzy7phr7iYzeKUcz9WOZ6m1ZP9+WQJFzlFBYBtoSXPXHVKZc8K0sa5n5l3D4ueUJx9u4HImBz+Tp+0sCvtCfxbRkjLrdIC1Vl+rui9L6xBaH8ekrrZe4CEkvIy6+JNf2BSxqgShzDR253J4RFiZ+MOEYR0+DAxFjvBrdJNLq2x1qwrrUV+4r6jcsqlOzXEjyuMsydO0XLYyTP3mZL40Mrmb0M5yfKstlGjn754GiWz3v1fJFRLDpjipzGk+H3wvkC2ft8DmbI35Py0j15qvDndT9pR8UmWlmwDuJSLghToSlFElO45OurbnHedgL+FXIuiIOmxNE16QqbCQjyVBtbkNSg0lLXLMPd3d3uOzz+R9+j1n05yCjsXJsF Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. 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 --- mm/huge_memory.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index c5d11147b69ae..87c9fc48b7cfd 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1064,7 +1064,8 @@ int folio_memcg_alloc_deferred(struct folio *folio) static int __init thp_shrinker_init(void) { deferred_split_shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE | - SHRINKER_MEMCG_AWARE, + SHRINKER_MEMCG_AWARE | + SHRINKER_NONSLAB, "thp-deferred_split"); if (!deferred_split_shrinker) return -ENOMEM; -- 2.43.7