From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755765AbbBPPSA (ORCPT ); Mon, 16 Feb 2015 10:18:00 -0500 Received: from casper.infradead.org ([85.118.1.10]:56164 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754955AbbBPPR7 (ORCPT ); Mon, 16 Feb 2015 10:17:59 -0500 Date: Mon, 16 Feb 2015 16:17:51 +0100 From: Peter Zijlstra To: Huang Ying Cc: Jason Low , LKML , LKP ML , mingo@kernel.org, dave@stgolabs.net Subject: Re: [LKP] [mutex] 871a6bb4916: -1.8% will-it-scale.per_process_ops, -98.3% will-it-scale.time.voluntary_context_switches, +209.6% will-it-scale.time.involuntary_context_switches Message-ID: <20150216151751.GE5029@twins.programming.kicks-ass.net> References: <1423986414.5538.8.camel@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1423986414.5538.8.camel@intel.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Feb 15, 2015 at 03:46:54PM +0800, Huang Ying wrote: > FYI, we noticed the below changes on > > git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git locking/core > commit 871a6bb4916fef3123b6ff749b0dc82680fb0d2a ("mutex: In mutex_spin_on_owner(), return true when owner changes") > > > testbox/testcase/testparams: wsm/will-it-scale/performance-writeseek3 > > e07e0d4cb0c4bfe8 871a6bb4916fef3123b6ff749b > ---------------- -------------------------- > %stddev %change %stddev > \ | \ > 24972759 ± 2% -98.3% 417134 ± 9% will-it-scale.time.voluntary_context_switches > 2223 ± 49% +209.6% 6884 ± 10% will-it-scale.time.involuntary_context_switches > 542 ± 32% +91.3% 1037 ± 0% will-it-scale.time.system_time > 186 ± 30% +86.3% 347 ± 0% will-it-scale.time.percent_of_cpu_this_job_got > 26.11 ± 5% -22.7% 20.18 ± 2% will-it-scale.time.user_time > 0.09 ± 1% -18.2% 0.07 ± 1% will-it-scale.scalability > 783528 ± 0% -1.8% 769550 ± 0% will-it-scale.per_process_ops > 12.27 ± 10% +492.7% 72.73 ± 1% perf-profile.cpu-cycles.mutex_optimistic_spin.__mutex_lock_slowpath.mutex_lock.generic_file_write_iter.new_sync_write > 3.22 ± 26% +1718.0% 58.50 ± 1% perf-profile.cpu-cycles.osq_lock.mutex_optimistic_spin.__mutex_lock_slowpath.mutex_lock.generic_file_write_iter Do you have the results for more/different performance tests for this commit? Jason mentioned seeing +5% on one (fserver). So if, for multiple tests, we see an avg improvement, we might trade that for this one regression. If otoh we see a net negative, we'll have to go do something about this.