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Thu, 17 Jul 2025 20:30:14 -0700 (PDT) Message-ID: <729aa946-7609-890a-3a13-4b0a58359aaa@gmail.com> Date: Fri, 18 Jul 2025 11:30:03 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.15.0 Subject: Re: [PATCH] mm/mglru: Update MG-LRU proactive reclaim statistics only to memcg To: Yuanchu Xie Cc: akpm@linux-foundation.org, yuzhao@google.com, shakeel.butt@linux.dev, mhocko@kernel.org, lorenzo.stoakes@oracle.com, kinseyho@google.com, hannes@cmpxchg.org, gthelen@google.com, david@redhat.com, axelrasmussen@google.com, zhengqi.arch@bytedance.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hao Jia References: <20250717082845.34673-1-jiahao.kernel@gmail.com> From: Hao Jia In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: o9yxkbymtmz4ew9cw4yz85t3q7osmnny X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: EF0D5100006 X-Rspam-User: X-HE-Tag: 1752809415-372715 X-HE-Meta: U2FsdGVkX18Ql6KXVVxP9ZnE2yHMdpKLPv9UiNzT9jOo3y14c5Ql107OqMg2U/9LafZfF/2hoAqnYyRmb7RxDG7qZbmuRNuDYY+3UFzd8eRmqynYtRj8VRZ3eNslRBZ5iFcg8yZAtx7V6MfeqOpPzcvYCsv9dtw/+DHobSw5OMCsQnZsZvLpcSV14SaQBbN2kZddIAOzZ4+RvvDWwxz7jE96aHrB/XXt3Mr7uqhXbIh1VOq4PIW7zZ9wMSSt1a1rHMAPaF7XVhVzj+AxwBBS7y3d52jKO4IVqC90jCYu+XLArn29IUlaMkcLC/QUJ22xGx8GcRQV0+1OZpBFy54eTH3Q4OP8ZwatfN1KSj4ERd6CTLwEiFPOSAHMXETrzw/1IsztzLzz2OiosXmZuPedFwMzxd1Ww1Pe+T7Qhm8CTokAwJlhYxt5gDLSmTSr4oYp7RmsAh/el9DeQWzPPdNHzHNcNZkqdrB5F3jv8XFINjM2LY1MhFEEO0Sg6YlEgHV72LtgSkMrR8MzXJBw/nxgiIL0AD5MwNzdbt1fD6iqGEGZsjXNR8IXq6lWHZVLtVaW4NIB87xoT1w5oYzqnh6ajY6Jqf95Jwug00g3S4WT3DPO2dKaEU8YHq8cWcY+AnCn4Wi8QYq9EsRi01nTjrIJva+n5IshTf+ba9ybSTn5yDiKRahk4nIVXRwmJGPd+IManWpghq8drifCO8WTGJtj3dapM0U3VUMEhFobpDAYnVt1aKPvBpbdcwx28TyZGwESZ3pA4ym7/NN7maumv3KKksF5hKgBMYDb96WHYRZaQ5f/14EYR8q45UigFSIHfDl+mJ3lgDSnQm+mcRrChyx9NFkd8qSwvOiFXPawcZ7UE1hPBH33zhjJv0O4KtkYsVdUr9OfAI9Eb2Kcukst9l2LGy9uwbNWT9k/rlsyMILgg95+GGqSFeFzp63bwOOz2g64K8Ds9jYxG3OKLtP9h3a jHKTkbnV +Z3fVGVYuYHuu/dpNXQztLBrvSrAILeCU7Ty0uoVeR8TYe1wi0JCKu0THZV22XPINmsxgqrmje48YY6Z6ejsHPpmut+XCDmHujg0bCaOYlMqZvEbKNLIoG8GRx8cpEN3wR8HrGvWkOQMwiVCFvTSfW1lcsOgJCJJ8VOIZXqnhhx7/PeHe8ixSpjG8AY459YKsBc82pG8dzHyDbiH5fWKeKGGeMxoyEHJIwH0zLFCGqWfoJuFudwCIqc9CcKb2vpsDMIkcat1MKlnT7SbJlHbObznGws2f9fT6+9kE4qayxQsu7CVx2FL8WAQ/yAJBKcs7KQbpdBrCWIIlYn5qfQUnbAU4j9fRQQVYHmUSepBoIng5PdZAVvA206rIqdXTjrn1E/DJg1Z7Zs/F+xPLeddgrQHcH8ZcHHjprU4A5Ci/Svk8CqscaPFcFQ3EzPX14DajiHXokEye3ErWoGNlISWYlV19kq7imQAXH4nqpNgNAqaARTvZ2OkWMizllT5rRG9ydzi9bABOSFAsBwllmXERHNRhBa0ArVAX5gP6B3o/Hu1rfoZFf9COZK6T8UX6GQKlMsN8BRQm8/TvKKM7PzYx43kBIT2pL2DLF6QjANWH61nyGiA7MogluBkWmA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2025/7/18 04:18, Yuanchu Xie wrote: Hi Yuanchu, > Hi Hao, > > On Thu, Jul 17, 2025 at 1:29 AM Hao Jia wrote: >> >> From: Hao Jia >> >> Users can use /sys/kernel/debug/lru_gen to trigger proactive memory reclaim >> of a specified memcg. Currently, statistics such as pgrefill, pgscan and >> pgsteal will be updated to the /proc/vmstat system memory statistics. > > This is a debugfs interface and it's not meant for use in production > or provide a stable ABI. Does memory.reclaim not work for your needs? > No, I am comparing the two interfaces. Thanks for your reminder, but I want to use this interface run_aging() to age folios, and separate proactive memory reclamation from multiple walk_mm() by combining it with BIT(LRU_GEN_MM_WALK). For example, user-space agent, enable LRU_GEN_MM_WALK, and then trigger run_aging(). Then turn off LRU_GEN_MM_WALK and use cgroup.reclaim to trigger proactive reclamation. Avoid the long latency caused by walk_mm(). Maybe it would be more reasonable to put walk_mm() in workqueues? I don't know if my idea is reasonable, any suggestions are welcome. Thanks, Hao > I'm not against the change; I just hope you don't depend on it > continuing to exist/behave a certain way. > > Shakeel's comment is accurate. The lru_gen interface uses the internal > memcg id which is not usually used to interface with the userspace. > Reading this file does show the cgroup path and memcg id association. > >> >> This will confuse some system memory pressure monitoring tools, making >> it difficult to determine whether pgscan and pgsteal are caused by >> system-level pressure or by proactive memory reclaim of some specific >> memory cgroup. >> >> Therefore, make this interface behave similarly to memory.reclaim. >> Update proactive memory reclaim statistics only to its memory cgroup. >> >> Signed-off-by: Hao Jia > > The patch looks okay to me too. > > Thanks, > Yuanchu