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[198.145.29.99]) by mx.google.com with ESMTPS id m4si30718396pfb.134.2019.05.22.12.33.15 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 May 2019 12:33:15 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=VBk26ou6; spf=pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from localhost.localdomain (c-73-223-200-170.hsd1.ca.comcast.net [73.223.200.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 580E22081C; Wed, 22 May 2019 19:33:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558553595; bh=6qKU+B/1sLWcpfUDU4BTAWbTNsNaXNjYvd5KmtBg83g=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=VBk26ou6dZVk+4grpdhByS7aR1CjwbLWb4irfv9IlBIyD9Jhwsri03YCDRfCP1B6k Cpsw+1GSshZluumcBnSbDzcBwMLtQgvuul3Shs1xU0YX9290UpJ6s1H6qbzj5wnrJ2 76gsPU1MsWwvAtWMibxKbokqGx4V8/C9PCvxy4s8= Date: Wed, 22 May 2019 12:33:14 -0700 From: Andrew Morton To: Yafang Shao Cc: 9erthalion6@gmail.com, mhocko@suse.com, shaoyafang@didiglobal.com, linux-mm@kvack.org Subject: Re: [PATCH v2] mm/vmscan: expose cgroup_ino for memcg reclaim tracepoints Message-Id: <20190522123314.e17fc708ff6548b9b621d6ad@linux-foundation.org> In-Reply-To: <1557649528-11676-1-git-send-email-laoar.shao@gmail.com> References: <1557649528-11676-1-git-send-email-laoar.shao@gmail.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 Sun, 12 May 2019 16:25:28 +0800 Yafang Shao wrote: > We can use the exposed cgroup_ino to trace specified cgroup. > > For example, > step 1, get the inode of the specified cgroup > $ ls -di /tmp/cgroupv2/foo > step 2, set this inode into tracepoint filter to trace this cgroup only > (assume the inode is 11) > $ cd /sys/kernel/debug/tracing/events/vmscan/ > $ echo 'cgroup_ino == 11' > mm_vmscan_memcg_reclaim_begin/filter > $ echo 'cgroup_ino == 11' > mm_vmscan_memcg_reclaim_end/filter Seems straightforward enough. But please explain the value of such a change. What is wrong with the current situation and how does this change improve things? A simple use-case scenario would be good. I can guess why it is beneficial, but I'd rather not guess! Thanks.