From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-61.mta1.migadu.com [95.215.58.61]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 009EC3403E0 for ; Tue, 8 Sep 2026 03:41:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.61 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788838909; cv=none; b=IrZZ0q9I6gnY50h6PaThf9Owrm4fXLiGVAajrEr+jFn5MyNTZTKXXmUw+XRSkThpDwnpHVK+YXsV0P/tSEgeOPGNfQafw7GewEOFtouJfxwr74OGQq10IAR0jduq0rMBF33WrQccE2bhuvWO5h5vxd3zk96I8VMkOt71Qw8gxHE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788838909; c=relaxed/simple; bh=nz77HtyT1E9SAWjePbr3tA2EChE5CYUU4QmxpcLu6z0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=NkEs5fUToRQ7BrqVD4Ae7z/WSnR1OTocjK7jps2uk/AYgaxule7O4UyS5hmGecOzNbbxy//LQpMfrODj02aZ2WeAaV77SJYSwAXQ+jjZDZM0+TdBqXHF8rcRM6JxghwzEW6LNQE9IEuUvL5qkBnLdDOjz7IbiTlvJwVdm41wMDc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=aPWfvkUy; arc=none smtp.client-ip=95.215.58.61 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="aPWfvkUy" X-Envelope-To: cgroups@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=nz77HtyT1E9SAWjePbr3tA2EChE5CYUU4QmxpcLu6z0=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788838889; v=1; x=1789443689; b=aPWfvkUyXzY8VsxxwbswTIE7mQi0QqNICMmJpbd2tXskxvLDZKEOYQx3vgi5se5zLSKwuWmE jPGflZ0Aya0Eg3IzmXnW2TfS8dEpng4zMiT24uJurJO2O42/blZVzDhX5Zijq2p9LbneGDCHQLl 9ccgDzalSG/ZZxcAalDMQPGo= X-Envelope-To: cgroups@vger.kernel.org Received: by mta12.migadu.com with ESMTPS id 074fc28e9a8b36e4; Tue, 08 Sep 2026 03:41:29 +0000 X-Mizu-Trace-ID: 074fc28e9a8b36e4 X-Migadu-Flow: FLOW_OUT From: Hui Zhu To: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , David Hildenbrand , Qi Zheng , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Hui Zhu Subject: [PATCH v4 0/4] mm: workingset: fix the shadow node budget under MGLRU Date: Tue, 8 Sep 2026 11:41:10 +0800 Message-ID: X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Hui Zhu Commit 7404bd37cfbe ("mm: workingset: use lruvec_lru_size() to get the number of lru pages") broke the workingset shadow node budget under MGLRU: lruvec_lru_size() reads mz->lru_zone_size, which MGLRU never maintains, so count_shadow_nodes() sees the evictable LRU lists as empty and the shadow shrinker reclaims eviction tokens almost as fast as they are created, losing thrashing protection. Patch 1 extends the dying-mcg stat redirection (previously cgroup v1 only) to all hierarchies, addressing the reparenting race that motivated 7404bd37cfbe. Patch 2 then switches count_shadow_nodes() back to lruvec_page_state_local(), which both classic LRU and MGLRU maintain. Patch 3 recovers the performance. Patch 1 added an unconditional rcu_read_lock() to the stat update fast path; patch 3 checks memcg_is_dying() first and takes the RCU lock only on the rare dying path. Patch 4 closes an accounting gap that patch 2 makes visible: on cgroup v2, reparent_state_local() never moves the dying memcg's non-hierarchical lruvec stats to the parent, so the parent receives the uncharges without the matching charges and its state_local underflows. Patch 4 reparents those stats, mirroring cgroup v1. Performance testing =================== The test script and the raw results are available at [1]. Environment: 10-vCPU QEMU guest, 8 GiB RAM, cgroup v2; 7 runs per configuration, medians reported. Workloads: w1-anon-churn: single-threaded anon fault/charge loop in a memcg (MADV_DONTNEED + re-fault, no reclaim). Every touch is a real fault with charge and memcg stat updates, so it stresses exactly the fast path patch 1 changes. w2-file-churn: file read loop under memory.high pressure (reclaim-bound, noisier). w3-reparent: reparent accounting sanity check. w1-anon-churn (pages/s): classic LRU MGLRU base 4393028 4377122 patches 1-2 4385996 (-0.2%) 4352887 (-0.6%) patches 1-3 4381832 (-0.3%) 4377053 (+0.0%) w2-file-churn (MB/s): classic LRU MGLRU base 8277 8226 patches 1-2 8226 (-0.6%) 8123 (-1.3%) patches 1-3 8157 (-1.4%) 8294 (+0.8%) w3-reparent passed on all kernels. The small overhead visible with patches 1-2 comes from the redirection added by patch 1; patch 3 brings w1 back to the base level in both LRU configurations. The remaining differences are within run-to-run noise. Patch 4 only touches the memcg offline path and is not exercised by these workloads. [1] https://gist.github.com/teawater/32f373ec41d185d840455eb167321a5a Changelog: v4: According to the comments of Andrew, Fix "follow-up patch" to "preceding patch" in the commit message to match the reordered series. According to the comments of Sashiko, add patch 4 to reparent the non-hierarchical lruvec stats on cgroup v2 to fixing the state_local underflow. v3: According to the comments of Shakeel, reorder the series per review, add Fixes/Cc stable and the user-visible impact to patch 1. Hui Zhu (4): mm: memcg: redirect stats updates of dying memcgs for all hierarchies mm: workingset: use lruvec_page_state_local() to count lru pages mm: memcg: skip the RCU lock when the memcg is not dying mm: memcg: reparent non-hierarchical lruvec stats on cgroup v2 mm/memcontrol-v1.h | 5 ++-- mm/memcontrol.c | 72 +++++++++++++++++++++++++--------------------- mm/workingset.c | 5 ++-- 3 files changed, 45 insertions(+), 37 deletions(-) -- 2.43.0