From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 E5A9A70830 for ; Tue, 9 Sep 2025 02:48:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757386117; cv=none; b=Tu+0J7MwDeYF15xckF8NnRVvTj+pNnKqGGsaJIFFd5NQSIg+q0/+xysFm8UKdEqSyH9L2xVDaEIAqOI2wfT/xp2A8do9EPuB9seADh9pDkG8Cecs2KmZ80WBSO+u71kxhU6RBYs5renlCTmRpaB0R5dfJzqwpeAcFrwHW2SeTlE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757386117; c=relaxed/simple; bh=Cf9cc8tV8BPB2LDfLPq5iIKTU42zE8bWm8jRbfM9Azs=; h=Date:To:From:Subject:Message-Id; b=HF5VushZbpHSs7ZDV4/PxZJxKamr6CBWq+mJwhYZ/opiVQvh3610kAfZ00rvxzs1KkGOHaPv/MWvjJ6WcBGkPVvnfyO4ZiwkC8d/uT/eWSX7+ZP7YyokFcpq/GnTyydH5zt5hBoWDvrQ/DEjrP0nt753gX/FWIW1xe2n9vXV58s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=mri48Sl3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="mri48Sl3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 51F2BC4CEF1; Tue, 9 Sep 2025 02:48:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1757386116; bh=Cf9cc8tV8BPB2LDfLPq5iIKTU42zE8bWm8jRbfM9Azs=; h=Date:To:From:Subject:From; b=mri48Sl3q/oXKOkzy7Rxk0lCUQnUIkZfyXTUJ3XGVmM9tgkR/+POM/Fx22f2r/N66 KpUiHRRiLNHTT+sbGL+Pb24xn2sNX+iyyYh7MVuIXr4lJpd99pN07P2AifWfFzBp35 zUXnJ4Ks3ZM/G1TWO01uNaxvtPavIe7SEtF0ATT8= Date: Mon, 08 Sep 2025 19:48:35 -0700 To: mm-commits@vger.kernel.org,zhengqi.arch@bytedance.com,yuanchu@google.com,weixugc@google.com,songmuchun@bytedance.com,shakeel.butt@linux.dev,roman.gushchin@linux.dev,mhocko@suse.com,lorenzo.stoakes@oracle.com,hannes@cmpxchg.org,david@redhat.com,axelrasmussen@google.com,cuishw@inspur.com,akpm@linux-foundation.org From: Andrew Morton Subject: + disable-demotion-during-memory-reclamation.patch added to mm-new branch Message-Id: <20250909024836.51F2BC4CEF1@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm: disable demotion during memory reclamation has been added to the -mm mm-new branch. Its filename is disable-demotion-during-memory-reclamation.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/disable-demotion-during-memory-reclamation.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: cuishiwei Subject: mm: disable demotion during memory reclamation Date: Tue, 9 Sep 2025 09:21:41 +0800 I've found an issue while using CXL memory. My machine has one DRAM NUMA node and one CXL NUMA node: node 1 cpus: 96 97 98 99... - dram Numa node node 1 size: 772048 MB node 1 free: 759737 MB node 3 cpus: - CXL memory Numa node node 3 size: 524288 MB node 3 free: 524287 MB 1.enable demotion echo 1 > /sys/kernel/mm/numa/demotion_enabled 2.Execute a memory allocation program in a memcg cgexec -g memory:test numactl -N 1 ./allocate_memory 20 - allocate 20G memory numastat allocate_memory： Node 0 Node 1 Node 3 --------------- --------------- --------------- Huge 0.00 0.00 0.00 Heap 0.00 0.00 0.00 Stack 0.00 0.01 0.00 Private 0.05 20481.56 0.01 3.Setting the memory cgroup memory limit to be exceeded echo 15G > /sys/fs/cgroup/test/memory.max numastat allocate_memory： Node 0 Node 1 Node 3 --------------- --------------- --------------- Huge 0.00 0.00 0.00 Heap 0.00 0.00 0.00 Stack 0.00 0.01 0.00 Private 0.00 4011.54 10560.00 This happens because demotion was enabled, when the memcg's memory limit was exceeded, memory from the DRAM NUMA node was first migrated to the CXL NUMA node. After that, a memory reclaim was performed, which was unnecessary. When a memory cgroup exceeds its memory limit, the system reclaims its cold memory.However, if /sys/kernel/mm/numa/demotion_enabled is set to 1, memory on fast memory nodes will also be demoted to slow memory nodes. This demotion contradicts the goal of reclaiming cold memory within the memcg.At this point, demoting cold memory from fast to slow nodes is pointless;it doesn't reduce the memcg's memory usage. Therefore, we should set no_demotion when reclaiming memory in a memcg. Link: https://lkml.kernel.org/r/20250909012141.1467-1-cuishw@inspur.com Signed-off-by: cuishiwei Cc: Axel Rasmussen Cc: David Hildenbrand Cc: Johannes Weiner Cc: Lorenzo Stoakes Cc: Qi Zheng Cc: Shakeel Butt Cc: Wei Xu Cc: Yuanchu Xie Cc: Michal Hocko Cc: Roman Gushchin Cc: Muchun Song Signed-off-by: Andrew Morton --- mm/vmscan.c | 1 + 1 file changed, 1 insertion(+) --- a/mm/vmscan.c~disable-demotion-during-memory-reclamation +++ a/mm/vmscan.c @@ -6717,6 +6717,7 @@ unsigned long try_to_free_mem_cgroup_pag .may_unmap = 1, .may_swap = !!(reclaim_options & MEMCG_RECLAIM_MAY_SWAP), .proactive = !!(reclaim_options & MEMCG_RECLAIM_PROACTIVE), + .no_demotion = 1, }; /* * Traverse the ZONELIST_FALLBACK zonelist of the current node to put _ Patches currently in -mm which might be from cuishw@inspur.com are disable-demotion-during-memory-reclamation.patch