From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 697DC3E763E for ; Thu, 17 Sep 2026 05:02:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789621325; cv=none; b=QOHEdao1qwrUAMU1G/o6XH1uDtzPEn3CSPmkjfKmuVbxQsn29uPLYPiLG0yN/PQ8W9fhiNQmUKIa+dLhnz3Ydq55CNn0X2HNFM/FWN+1eLWi0s0v3/yODfk5n79fuxgmRQXynDYsUsLny1kKbjoM1EEV5bEFSx6hKeO5WdFa5Os= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789621325; c=relaxed/simple; bh=7Ug1SAYYOU4Mr0AvtJTXMQHk0SIaG3qDXSxibuDxnCU=; h=Date:To:From:Subject:Message-Id; b=URRjqZYB0GQjoLdidbV29YTJ9FG7p8mdYKgDxwib5MQtDH6ToC0qyfMkZ8YaH3L7JOmj3/PpPtoQy/re1Lee9rUi5XNy3y4xWofGf/3n0M3jxSYoGDpWP/hZ/sFKScMf0kXbBPSMwLmNqI6KdDgMvHRZ4sd+IHRfo8S22+Etsd0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=IA6HnED5; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="IA6HnED5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0F8891F000FF; Thu, 17 Sep 2026 05:02:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1789621324; bh=+z7AvvFh29sSlrkDyBojkqjnPSQZz1GzNU8B9EFRz9o=; h=Date:To:From:Subject; b=IA6HnED5XGX/lFzFtwiotBYAKxaBzQU86tnibm6Ux4HFWoIArLlhYIf+WW1qLVeAk C6OQTM13E2b/4PbB45IinF0jqVxRgKccWq5kv2htK9R4EroVWSNOou6RQB54py3kkq cqRGK5NWFJ2VVUC0lnuKYDGiy+SWAxO9Zv6vl9PA= Date: Wed, 16 Sep 2026 22:02:03 -0700 To: mm-commits@vger.kernel.org,zhuhui@kylinos.cn,akpm@linux-foundation.org From: Andrew Morton Subject: [to-be-updated] mm-memcg-skip-the-rcu-lock-when-the-memcg-is-not-dying.patch removed from -mm tree Message-Id: <20260917050204.0F8891F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm: memcg: skip the RCU lock when the memcg is not dying has been removed from the -mm tree. Its filename was mm-memcg-skip-the-rcu-lock-when-the-memcg-is-not-dying.patch This patch was dropped because an updated version will be issued ------------------------------------------------------ From: Hui Zhu Subject: mm: memcg: skip the RCU lock when the memcg is not dying Date: Fri, 4 Sep 2026 17:45:56 +0800 get_non_dying_memcg_start() takes rcu_read_lock() on every stat update, but the lock only protects the upward walk to a non-dying ancestor, which happens solely while a memcg is being offlined. The dying check itself reads the CSS_DYING flag of a memcg the caller already holds a reference to, so it is safe without the lock. Check memcg_is_dying() first and return immediately when the memcg is alive, taking the RCU lock only on the rare dying path. On an anon fault/charge churn workload in a memcg this recovers the ~0.6% overhead added by the previous patch (4368077 vs 4343159 pages/s before, back to ~4377000 pages/s after). Link: https://lore.kernel.org/0db657472c5278b2e2b87fbca7590b47ca520303.1788514750.git.zhuhui@kylinos.cn Signed-off-by: Hui Zhu Signed-off-by: Andrew Morton Acked-by: Shakeel Butt Cc: Axel Rasmussen Cc: Barry Song Cc: David Hildenbrand Cc: Johannes Weiner Cc: Kairui Song Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Wei Xu Cc: Yuanchu Xie --- mm/memcontrol.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) --- a/mm/memcontrol.c~mm-memcg-skip-the-rcu-lock-when-the-memcg-is-not-dying +++ a/mm/memcontrol.c @@ -881,6 +881,17 @@ static long memcg_state_val_in_pages(int static inline struct mem_cgroup * get_non_dying_memcg_start(struct mem_cgroup *memcg, bool *rcu_locked) { + /* + * Fast path: the caller holds a reference to @memcg, so reading + * its CSS_DYING flag without the RCU lock is safe. The RCU lock + * is only needed to walk up to a non-dying ancestor, which + * happens only while a memcg is actually being offlined. + */ + if (!memcg_is_dying(memcg)) { + *rcu_locked = false; + return memcg; + } + rcu_read_lock(); *rcu_locked = true; @@ -892,6 +903,9 @@ get_non_dying_memcg_start(struct mem_cgr static inline void get_non_dying_memcg_end(bool rcu_locked) { + if (!rcu_locked) + return; + rcu_read_unlock(); } _ Patches currently in -mm which might be from zhuhui@kylinos.cn are mm-vmstat-annotate-data-race-for-per-cpu-pageset-fields.patch