From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shakeel Butt Subject: [PATCH] memcg: expose root cgroup's memory.stat Date: Fri, 8 May 2020 10:06:30 -0700 Message-ID: <20200508170630.94406-1-shakeelb@google.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=BNj9Z6arsMIsAVorXWKDmEgiJTCFic/kTsm/LbalWf8=; b=cWd8iE2BULhsuzGBLhEY2ZykQklRkw+mBHU/UMcTu++CnkoD19Vwbyu9ZXAq+Hvjm3 eKnZGz1RV/GJTLIu+z8x3At8UyE3gi6rwQ2pKfNtHATsjtlhYJDACFP5XqkImrYM4REU o+Cqrm1AXu9jkv3QQPIjtPsZLxcHhocu8oRlAndWoiWFd4gsXxte2X28wRZ3L6ck0q1U fbOVueB3efN0mUTnXzEm1dz447Ij8sdDOPniira68MQcgRhGm0xO5FH37HOmdlVHeoTl 61LMlaKmNqqB299IJUdkAwrLrEj457QuNL3sBadYKkE8dCyJi8rIl7w0ts4Nwgy2jbxC Z4MQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Mel Gorman , Johannes Weiner , Roman Gushchin , Michal Hocko Cc: Andrew Morton , Yafang Shao , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Shakeel Butt One way to measure the efficiency of memory reclaim is to look at the ratio (pgscan+pfrefill)/pgsteal. However at the moment these stats are not updated consistently at the system level and the ratio of these are not very meaningful. The pgsteal and pgscan are updated for only global reclaim while pgrefill gets updated for global as well as cgroup reclaim. Please note that this difference is only for system level vmstats. The cgroup stats returned by memory.stat are actually consistent. The cgroup's pgsteal contains number of reclaimed pages for global as well as cgroup reclaim. So, one way to get the system level stats is to get these stats from root's memory.stat, so, expose memory.stat for the root cgroup. from Johannes Weiner: There are subtle differences between /proc/vmstat and memory.stat, and cgroup-aware code that wants to watch the full hierarchy currently has to know about these intricacies and translate semantics back and forth. Generally having the fully recursive memory.stat at the root level could help a broader range of usecases. Signed-off-by: Shakeel Butt Suggested-by: Johannes Weiner --- mm/memcontrol.c | 1 - 1 file changed, 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 05dcb72314b5..c300d52c07a5 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6230,7 +6230,6 @@ static struct cftype memory_files[] = { }, { .name = "stat", - .flags = CFTYPE_NOT_ON_ROOT, .seq_show = memory_stat_show, }, { -- 2.26.2.645.ge9eca65c58-goog