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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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 33DB01C0007 X-Stat-Signature: 577gn8bdt9mrkf8pm1wpqc1ecbm1ymmu X-HE-Tag: 1779766783-888421 X-HE-Meta: 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 7YSZlQ7O 1VqGv6tkLcTsWtjGxZjWKcQs9PVZDASJgWGNNlP3LfpDVRQYLy9s/E7RdkaseoHwT1w+sKWl0K6dVi57gQ7e0EXpn5c6WItiel2ACPBWkEqosO4Z1mXWrzsI+VPfKFwyjyFgcb/VXkf3OGuIQhiohOHi8398FLLNRZ15IeQC6Am/x8cklmxGCC2RUBkYGenYohUqmEcH9dy1fo7rhh+StJutd7qsVehBd4EPOr8e9UX38vBYAE1+A/whgSFQG7gL1rf8c7ujjTUL9G/7hYncqFVorxRvaoZMKd7pF4bNLimEQcRwFPJfNiPD99YWB1zXNQ4Nl4x+HWCPNH0d9nrtHfdZqN7rz/RrOClfHJw9lnlnQxcQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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