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Received: from 30.74.144.153(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0XCnt3KH_1791948936 cluster:ay36) by smtp.aliyun-inc.com; Wed, 14 Oct 2026 11:35:37 +0800 Message-ID: <303ad1b0-c2a9-4608-9fec-e94d592f4593@linux.alibaba.com> Date: Wed, 14 Oct 2026 11:35:36 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: vmscan: don't count per-node proactive reclaim as memory pressure To: Vernon Yang , akpm@linux-foundation.org, david@kernel.org, kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, baoquan.he@linux.dev, hannes@cmpxchg.org, mhocko@kernel.org, ljs@kernel.org, roman.gushchin@linux.dev, dave@stgolabs.net Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vernon Yang , stable@vger.kernel.org References: <20261012022917.1102467-1-vernon2gm@gmail.com> From: Baolin Wang In-Reply-To: <20261012022917.1102467-1-vernon2gm@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 23E6B180004 X-Rspam-User: X-Rspamd-Server: rspam12 X-Stat-Signature: 6zhoiq6199g7ypzjbcisncyum7dhs9gp X-HE-Tag: 1791948942-679274 X-HE-Meta: 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 lIaRzLdh fjLH5HqhXeKgtcNxPsprMpdWHLftVm/4+8UK2DFkXhbJtXWwTyJQQMujoamzaxgSzKR4Yzm1tBE2S0BmpXFnKWUChpQCil9P6MCRw9ABLyabB7mTEloMCcDJ3rZywbFCY4Gcdy9AwudpygT6fYSH9LS6LzdJWr9O41jCKJxfMRnQnDaVWMvULrICN4ty+jNA7qDfI5tiTku0VodzIX5s4qrEuUAKRYQzfUxkNLjYCWZWkS2RmOTkmDk7zuzzumHqLz5OjnsC2+0tjRbxNJervNDPAge7gW5SxYBbR/Whyv9ar2l3SzsvWecuLS2K539nALqUIQhwGfNvOpl62lFRsoLkOo3d9RXNTLE+T Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/12/26 10:29 AM, Vernon Yang wrote: > From: Vernon Yang > > When the cgroup has no memory pressure at all, writing to > /sys/devices/system/nodeX/reclaim triggers proactive reclaim on > NUMA node, causing increase in the writer cgroup's memory PSI. > > Due to this reclaim is performed in the context of the write(), > accounted as memory pressure on the writer, like > commit e22c6ed90aa9 ("mm: memcontrol: don't count limit-setting reclaim > as memory pressure"). This is unexpected, the similar scenarios (e.g. > senpai) will continue to occur, only this time it is for the > /sys/devices/system/nodeX/reclaim knob. > > The Documentation/ABI/stable/sysfs-devices-node documentation also > notes that "This interface is equivalent to the memcg variant." > > This patch unifies the semantics of the memcg and node interfaces: > per-node proactive reclaim is no longer counted as memory pressure, > and the per-node proactive reclaim interface no longer produces > phantom pressure. > > I ran demo[1] that performs per-node proactive reclaim 10000 times > in qemu, writer cgroup memory.pressure as follows: > > without patch: > > some avg10=31.53 avg60=13.42 avg300=3.31 total=10602985 > full avg10=31.53 avg60=13.42 avg300=3.31 total=10602985 > > with patch: > > some avg10=9.59 avg60=3.41 avg300=0.81 total=2686221 > full avg10=9.59 avg60=3.41 avg300=0.81 total=2686221 > > [1] https://github.com/vernon2gh/app_and_module/tree/main/reclaim_node_psi > > Fixes: b980077899ea ("mm: introduce per-node proactive reclaim interface") > Cc: stable@vger.kernel.org > Signed-off-by: Vernon Yang > --- LGTM. Reviewed-by: Baolin Wang