From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-173.mta1.migadu.com (out-173.mta1.migadu.com [95.215.58.173]) (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 24F5A383C94 for ; Tue, 26 May 2026 03:39:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779766785; cv=none; b=IMDZtUpNQ5dp94TCKRFl9LaSg4oAv/U/IifM97e/g6Hrv8Cx7DhqXGawEcn1TzALnwDkQNtAdY1v7vfXMJnkvEeDzkGzlKwa1fv0n+Zj4B9NBg0LozzgCWIdWAQzh32Lk+7fQr5TDywErmt3F+chj2L7tOoIK1iu/gjcm+wXVdw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779766785; c=relaxed/simple; bh=FpjTxyyhAQF6oHErw7PR3RR7bFsoWA2ESqzzjhvaf88=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=dYVJmeBIybFb6Zck9qd1utz8Vp+N5ipd1M19b+c21wda0urcSn9HOdkIor3RvcqnRYFZyftKX6ohVh6Zc/OPRAlMbPgM6qvgOOUaPphv1p76fxbDIJdEU7Nl4WqttdJZpy4Xx+M05el0WbXFzcdyn3DeitTVKYRG6GtXzJPk+LU= 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=sreSYi4o; arc=none smtp.client-ip=95.215.58.173 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="sreSYi4o" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1779766781; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=nvpqW7ibe5xkt1e+Ex6u6rO4+BgyyQ77/2aNrwatCuc=; b=sreSYi4oA1LA9VSAfRsj2bnDuCMWeS7fx0WkQeDjzmeSKORaGFS5uJNnJ9+o5F54XEjqeu XHdsIQKAgEp74gbMuuzupg0+YXI2+x4jjhF41jbgBcjaZapr8lSkFa2DFnwfasRLhuXXY+ VMA4KLKdusErJ+/JfJck9QXzN8D50wU= From: Shakeel Butt To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Qi Zheng , Alexandre Ghiti , Joshua Hahn , Harry Yoo , David Laight , Meta kernel team , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel test robot Subject: [PATCH v3 0/4] memcg: shrink obj_stock_pcp and cache multiple objcgs Date: Mon, 25 May 2026 20:39:27 -0700 Message-ID: <20260526033931.1760588-1-shakeel.butt@linux.dev> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Commit 01b9da291c49 ("mm: memcontrol: convert objcg to be per-memcg per-node type") split a memcg's single obj_cgroup into one per NUMA node so that reparenting LRU folios can take per-node lru locks. As a side effect, the per-CPU obj_stock_pcp -- which caches a single cached_objcg pointer -- thrashes on workloads where threads of the same memcg run on different NUMA nodes. The kernel test robot reported a 67.7% regression on stress-ng.switch.ops_per_sec from this pattern. Commit d0211878ce06 ("memcg: cache obj_stock by memcg, not by objcg pointer") landed as a temporary fix by treating sibling per-node objcgs as equivalent for the cache lookup, intended to be reverted once per-node kmem accounting is introduced. This series takes a more general approach: cache multiple objcgs per CPU using the multi-slot pattern memcg_stock_pcp already uses, so the per-node objcg variants of one memcg can all coexist in the stock without ever forcing a drain. The temporary fix can then be reverted. To avoid increasing the per-CPU cache footprint, the first three patches shrink the existing single-slot obj_stock_pcp fields. The final patch converts cached_objcg and nr_bytes into NR_OBJ_STOCK=5 slot arrays and reorders the struct so the entire consume/refill/account hot path fits within a single 64-byte cache line on non-debug 64-bit builds (verified with pahole). Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202605121641.b6a60cb0-lkp@intel.com Fixes: 01b9da291c49 ("mm: memcontrol: convert objcg to be per-memcg per-node type") Tested-by: kernel test robot Shakeel Butt (4): memcg: store node_id instead of pglist_data pointer memcg: uint16_t for nr_bytes in obj_stock_pcp memcg: int16_t for cached slab stats memcg: multi objcg charge support mm/memcontrol.c | 214 +++++++++++++++++++++++++++++++++++------------- 1 file changed, 157 insertions(+), 57 deletions(-) -- Changes since v2: http://lore.kernel.org/20260522011908.1669332-1-shakeel.butt@linux.dev - Fix comments (Muchun & Qi) - Simplify code (David Laight) - Fix handling of archs with base page size larger than 256 KiB (Sashiko) Changes since v1: http://lore.kernel.org/20260520053123.2709959-1-shakeel.butt@linux.dev - Collected review tags (Harry & Muchun) - Fix comparison operators (Harry) - Use round robin for drain 2.53.0-Meta