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V" , Yosry Ahmed Content-Type: text/plain; charset="us-ascii" X-Rspamd-Queue-Id: 4D64020005 X-Stat-Signature: 8n3i6fx9cbqbi1b34jn8k1f8cxwooq7n X-Rspam-User: Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=p1NA6cOy; spf=pass (imf03.hostedemail.com: domain of 31tCFYggKCKkbQJTNNUKPXXPUN.LXVURWdg-VVTeJLT.XaP@flex--shakeelb.bounces.google.com designates 209.85.128.202 as permitted sender) smtp.mailfrom=31tCFYggKCKkbQJTNNUKPXXPUN.LXVURWdg-VVTeJLT.XaP@flex--shakeelb.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspamd-Server: rspam09 X-HE-Tag: 1652936909-61816 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: On Thu, May 19, 2022 at 04:08:15AM +0530, Vaibhav Jain wrote: > [1] Provides a way for user-space to trigger proactive reclaim by introducing > a write-only memcg file 'memory.reclaim'. However reclaim stats like number > of pages scanned and reclaimed is still not directly available to the > user-space. > > This patch proposes to extend [1] to make the memcg file 'memory.reclaim' > readable which returns the number of pages scanned / reclaimed during the > reclaim process from 'struct vmpressure' associated with each memcg. This should > let user-space asses how successful proactive reclaim triggered from memcg > 'memory.reclaim' was ? > > With the patch following command flow is expected: > > # echo "1M" > memory.reclaim > > # cat memory.reclaim > scanned 76 > reclaimed 32 > Yosry already mentioned the race issue with the implementation and I would prefer we don't create any new dependency on vmpressure which I think we should deprecate. Anyways my question is how are you planning to use these metrics i.e. scanned & reclaimed? I wonder if the data you are interested in can be extracted without a stable interface. Have you tried BPF way to get these metrics? We already have a tracepoint in vmscan tracing the scanned and reclaimed.