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Received: from banye.tbsite.net(mailfrom:qinyuntan@linux.alibaba.com fp:SMTPD_---0XAh0I06_1789027649 cluster:ay36) by smtp.aliyun-inc.com; Thu, 10 Sep 2026 16:07:30 +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 v3 3/4] mm: thp: restore SHRINKER_NONSLAB on the deferred split shrinker Date: Thu, 10 Sep 2026 16:07:21 +0800 Message-ID: <20260910080722.3961351-4-qinyuntan@linux.alibaba.com> X-Mailer: git-send-email 2.43.7 In-Reply-To: <20260910080722.3961351-1-qinyuntan@linux.alibaba.com> References: <20260910080722.3961351-1-qinyuntan@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: DA35716000D X-Stat-Signature: ojw31hau8khjn3b16ngigzkhid49qnx6 X-HE-Tag: 1789027653-435183 X-HE-Meta: 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 uVtIbQbj 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 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 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. The shrinker has carried SHRINKER_NONSLAB since commit 0a432dcbeb32 ("mm: shrinker: make shrinker not depend on memcg kmem") precisely so it would keep working with kmem accounting disabled. Commit fafaeceb89a5 ("mm: switch deferred split shrinker to list_lru") dropped it knowingly: under nokmem the list_lru collapses into a shared per-node list while __list_lru_add() still sets the shrinker bit on whichever memcg happens to add the first item, and with the flag set the shrinker would run twice per reclaim cycle [1]. NONSLAB-backed lrus keep their per-memcg lists under nokmem now, so the shrinker bit identifies the owning memcg again. Restore the flag. This was noticed by Michal during review of the patch "mm/list_lru: don't copy stale shrinker id from non-memcg-aware shrinkers" [2]. [1] https://lore.kernel.org/all/ah9PGv12mqai84ES@cmpxchg.org/ [2] 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 --- 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