From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755042Ab3A2IoH (ORCPT ); Tue, 29 Jan 2013 03:44:07 -0500 Received: from mail-bk0-f41.google.com ([209.85.214.41]:55287 "EHLO mail-bk0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754810Ab3A2IoE (ORCPT ); Tue, 29 Jan 2013 03:44:04 -0500 Date: Tue, 29 Jan 2013 09:44:00 +0100 From: Ingo Molnar To: Yuanhan Liu Cc: Huang Ying , Linus Torvalds , David Howells , linux-kernel@vger.kernel.org, lkp@linux.intel.com Subject: Re: aim7 performance regression by commit 5a50508 report from LKP Message-ID: <20130129084400.GA5350@gmail.com> References: <20130129082537.GS12678@yliu-dev.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130129082537.GS12678@yliu-dev.sh.intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Yuanhan Liu wrote: > [...] Very nice measurements and analysis, thanks! > As stated above, anybody can have a chance to own the lock in > mutex once somebody release the lock. Well, there is only one > to own the lock in rwsem write lock, and the one is known > already: the one in the head of wait list. That would result > to more contention in rwsem write lock case, especially if the > one _will_ own the lock is not running now. I think we should allow lock-steal between rwsem writers - that will not hurt fairness as most rwsem fairness concerns relate to reader vs. writer fairness. Am I correct to assume that all relevant users in this workload are down_write() users? You can see the type of lock use in: perf record -g perf report I bet that allowing rwsem writer lock-steal would improve other workloads as well. Thanks, Ingo