From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-211.mta1.migadu.com [95.215.58.211]) (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 3921C3D25AD for ; Mon, 31 Aug 2026 09:46:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788169597; cv=none; b=G9iWwy/1JNbdBm49OugLllix/g/iZtEfHMBcgz8OhLZ4cfayeEZn4hBMvygV/jBVlzI9aJ8LJdd+W4cXGHxGjPhFAZXwcHDERIbrv2UrDr6X8FrnqBD+YWN9jkhO2djJBKOOeuipDSZDJ7ZjACOl+BQeRG1Pd1dZUjUzyAa/ayM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788169597; c=relaxed/simple; bh=AF4DD4VVRvODeKZk9FQinottqHGc5UMNhNCLJuS+ivE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=nDRA669dPfYagMQOKJys2412pmPKEab6gCaMhJdl17WqpaSegFZsevPnCNGeWYOPs0S1PxWL+NGUzzZWAgvfaxt9mKBQHv65WzT9Z5Olo8bRAqh9Ukq6X3ID8kBxCqAlj9wzdNRfaiW2vWSZcALiT90d7RA05n71N6VFleekAs8= 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=LVprdE3U; arc=none smtp.client-ip=95.215.58.211 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="LVprdE3U" X-Envelope-To: cgroups@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=AF4DD4VVRvODeKZk9FQinottqHGc5UMNhNCLJuS+ivE=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788169592; v=1; x=1788774392; b=LVprdE3Ub8HO29yourlyTGlfgZbpOFAnHCkNfh7v77RZgWe+bRfXJGw8ujZhmy9rzG5HAduv 4w1CWWR5yqy55Sqny5U3xmGEUxhKeY+NusZ3F73Tr7P3FHamp3KNBxfEEFr8lRa0OqMs+2BQOom 3EhfzPJjhDd7GRJM71l4B7so= X-Envelope-To: cgroups@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 22025baba8b5f51b; Mon, 31 Aug 2026 09:46:32 +0000 X-Mizu-Trace-ID: 22025baba8b5f51b 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 v2 0/3] mm: workingset: fix the shadow node budget under MGLRU Date: Mon, 31 Aug 2026 17:46:08 +0800 Message-ID: X-Mailer: git-send-email 2.53.0 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 switches count_shadow_nodes() back to lruvec_page_state_local(), which both classic LRU and MGLRU maintain. Patch 2 addresses the reparenting race that motivated 7404bd37cfbe: patch 1 makes cgroup v2 read state_local as well, so extend the dying-memcg stat redirection (previously cgroup v1 only) to all hierarchies. Patch 3 recovers the performance. Patch 2 added an unconditional rcu_read_lock() to the stat update fast path; patch 3 moves the dying check out of the RCU read-side critical section so the lock is only taken on the rare dying path. 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 2 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. Patch 2 alone shows a small overhead, most visible under MGLRU (-0.6% on w1); patch 3 brings w1 back to the base level in both LRU configurations. The remaining differences are within run-to-run noise. [1] https://gist.github.com/teawater/32f373ec41d185d840455eb167321a5a Hui Zhu (3): mm: workingset: use lruvec_page_state_local() to count lru pages mm: memcg: redirect stats updates of dying memcgs for all hierarchies mm: memcg: skip the RCU lock when the memcg is not dying mm/memcontrol.c | 30 ++++++++++++------------------ mm/workingset.c | 5 ++--- 2 files changed, 14 insertions(+), 21 deletions(-) -- 2.53.0