From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753299AbaHSPv2 (ORCPT ); Tue, 19 Aug 2014 11:51:28 -0400 Received: from mga14.intel.com ([192.55.52.115]:5763 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752063AbaHSPv1 (ORCPT ); Tue, 19 Aug 2014 11:51:27 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,895,1400050800"; d="scan'208";a="578819923" Date: Tue, 19 Aug 2014 23:51:25 +0800 From: Fengguang Wu To: Mel Gorman Cc: LKML , lkp@01.org Subject: Re: [mm] 3484b2de949: -56.2% vm-scalability.throughput, +9.3% turbostat.Pkg_W Message-ID: <20140819155125.GB2697@localhost> References: <20140819043252.GA8798@localhost> <20140819142925.GB10146@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20140819142925.GB10146@suse.de> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 19, 2014 at 03:29:25PM +0100, Mel Gorman wrote: > On Tue, Aug 19, 2014 at 12:32:52PM +0800, Fengguang Wu wrote: > > Hi Mel, > > > > We noticed the below vm-scalability performance/power regressions on > > commit 3484b2de9499df23c4604a513b36f96326ae81ad ("mm: rearrange zone > > fields into read-only, page alloc, statistics and page reclaim lines"). > > > > 24b7e5819ad5cbe 3484b2de9499df23c4604a513 testbox/testcase/testparams > > --------------- ------------------------- --------------------------- > > %stddev %change %stddev > > \ | / > > 9.95 ± 2% +69.1% 16.83 ± 5% brickland3/vm-scalability/300s-lru-file-mmap-read > > 2.32 ± 6% +229.4% 7.63 ± 5% brickland3/vm-scalability/300s-lru-file-readonce > > 12.27 ± 3% +99.4% 24.46 ± 5% TOTAL vm-scalability.stddev > > > > 24b7e5819ad5cbe 3484b2de9499df23c4604a513 > > --------------- ------------------------- > > 13882598 ± 0% -35.8% 8915310 ± 1% brickland3/vm-scalability/300s-lru-file-mmap-read > > 36379953 ± 1% -64.0% 13093373 ± 0% brickland3/vm-scalability/300s-lru-file-readonce > > 50262551 ± 0% -56.2% 22008683 ± 0% TOTAL vm-scalability.throughput > > > > > What units are these? It's completely unclear what is good and bad from the > figures. 300s-lru-file-mmap-read appears multiple times in this report, > each with different numbers beside them but little clue as to what they > mean or what I'm meant to be looking for :( Sorry the output format is a bit obscure: the stats names are after the "TOTAL" word, such as TOTAL vm-scalability.stddev, TOTAL vm-scalability.throughput, ... > This is the same patch that was reported as having a performance gain in > another set of tests from lkp so am a little confused. That can happen some times -- we've seen some commits to benefit some workloads while hurting some others. I'm now running more complete test set for the commit, hopefully can get some results tomorrow. > More importantly, as this patch is primary abougt cache misses it should > be very unlikely that it makes a noticable difference to IO as the > relative cost of a cache miss is so low. Similarly any difference it > makes to reclaim activity is likely to be a coincidence or due to test > variance. The test case creates tmpfs files and read them fast to exercise the LRU. So it's VM test and do not involve disk IO. Thanks, Fengguang