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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1779412763; 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=KKSfM/86lAA+qnVTKOkWKPhGo0U5csvRd25duVGKj3I=; b=IWeo9KvIh2h2scxfoFtPqMmlThWuSS+fc0Azgjk9KBgBln+0lCDine9do+NBHzpw32wWfO A8P4nUpQ/mg5sd+iIDcEK3sBSsvfcYvKTXJoQBNARtPJcIYQgw2C7nj1NvdjGrvC6pDtbz cFFDELWcQTzrHO/iJBwK7ER8TeCTNzM= From: Shakeel Butt To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Qi Zheng , Alexandre Ghiti , Joshua Hahn , Harry Yoo , Meta kernel team , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel test robot Subject: [PATCH v2 0/4] memcg: shrink obj_stock_pcp and cache multiple objcgs Date: Thu, 21 May 2026 18:19:04 -0700 Message-ID: <20260522011908.1669332-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 0B4E710000B X-Stat-Signature: zscn8d9y7utr3tbi3imcbdxoscmiaan3 X-Rspam-User: X-HE-Tag: 1779412764-528379 X-HE-Meta: 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 xXhhwlXP cIQGpD5tkj/jnOfuHUaCx1zk5f8IDFRv0MRlIkk9VhqDZna/uh6BwmKJlzuyyLBHod+myaZ7fx967UHTQp1Nh/pCjmTb7nlLRbkfGc6WzcUpkQFWFFHs8OD02sHA+GsruAiaNbNmofhGvQxMLD+A9He/CcWu6tqonjwcuiqux4GMjc3EhjmEzxQqqXc5klk5UR7okmlCnv5xS6z8VqtkBkeu7ii9YD+gZosUTHDqvExXTkHp8oUXwzlAfUXK/DnMoXS0ci+7kjRrJ/dzQkq4j486nHX5P69DFHEMiCmGMPcujP7yGKmwspHi8b7amdsljw+Uk5n1Sf4HhjHCl2JnFYdMEglpseDpNlgjsGck3laMh6OA= 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 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