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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1779254980; 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=w9644gpBoOdPB14uQ67yzVOzo6y2pa74KkqSttfHrQ0=; b=oOdT9QjkNL+aTBjlLReLdJ3EnXS+dfmLSkf1hJvCfaJRXr5TbQqGqYmnDT4sm8Vlg+lrJa ZBbuCyt9/riSrBjJHV7ewel8MUcet5SG9UxkNLjIfMGFZI3EIZVKm3q0Ge9ITu96Q6lVLE y+hO0sIKpsKasqvqEjtX6/uwcii3Mcs= 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 0/4] memcg: shrink obj_stock_pcp and cache multiple objcgs Date: Tue, 19 May 2026 22:29:00 -0700 Message-ID: <20260520052904.2673675-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: nn99nc3wtu8isqsgsde5icrbka5bkebd X-Rspam-User: X-Rspamd-Queue-Id: 2224A1A0004 X-Rspamd-Server: rspam07 X-HE-Tag: 1779254983-893274 X-HE-Meta: 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 RDJaHwkj cnWJDVBUohLtWaCJ/t2Q8YlOWBwiTvtKZ7n/mrBr3ovMRJHzxqvGafKtuNADvbnDb6085FSQfgIZEf228Vaap19PqTcCIL6T+IiI9lP2osF20LeULbLe8T35E/GfMMcb44hgUHrsWgnLSlvuihoDziiSg+iOGT2Qe3UDCMsmdSNPBqAyVMBb+gMcF2OPlq/pXbczUJbhTEsJUccnio62dbk/rpefUyabREwQcncge9NMT6ZqtmFQCe00ON4KJyex1cGkvPTfa0TxU7iRTQikgHUW2OvL96WfmTuacWulrAT8s+N2KZ+w/8LNKP2HOiYC6XticH0xcVQ8lxhM= 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(-) -- 2.53.0-Meta