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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Johannes Weiner , Yosry Ahmed , Nhat Pham , Chengming Zhou , Kairui Song , Shakeel Butt , Xunlei Pang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qinyun Tan Subject: [PATCH 1/2] mm: thp: restore SHRINKER_NONSLAB on the deferred split shrinker Date: Fri, 4 Sep 2026 11:35:02 +0800 Message-ID: <20260904033503.4067283-2-qinyuntan@linux.alibaba.com> X-Mailer: git-send-email 2.43.7 In-Reply-To: <20260904033503.4067283-1-qinyuntan@linux.alibaba.com> References: <20260904033503.4067283-1-qinyuntan@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: B0F25140008 X-Stat-Signature: b18ufaa9r43niyq4ywf3ck15a7sii1nf X-Rspam-User: X-HE-Tag: 1788492913-699734 X-HE-Meta: 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 2rwA+UC5 GfFh7YGcJXfGnhQLembpCxML3uUWiU9UyFhxW2ma91BvjQu98B0RfO1kgO8SJ0Pn3wh+kLkMClC7SiwscQSk/X+qZJkHPvTf3pxNSsffsiya5HT/WC8/MMod4tZpdi6vr8mJygpwtFzqUDYDnwqBKwvT2d6QTR+dCsdChrdnHvVLNgqHB/3fYHE/T+w9PpgSZpEyJXyWBT4C+IBTikTObgS80YzL6XIK0I+fho2Yi+V769Y0fv61EqqcOKq3xnQA+TK3NX/zQvNzMXgrLoRbLC829OwrGaS8HmX1QdofimnfqpHVsNWkhBHVDsyy4hSyovVK7Cmxsy2h74apIWZqb8ivAxQetzWG23wWanURcsz37aG6J/SxN8LwG5MTZwfknxIKb8R4H5EGqv1717KywxJC3Yq1d4mXGnd+8 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 --- 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 644d6905b49cc..16f9aa5b2d077 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1022,7 +1022,8 @@ 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