From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758645AbZBYDu3 (ORCPT ); Tue, 24 Feb 2009 22:50:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754016AbZBYDuQ (ORCPT ); Tue, 24 Feb 2009 22:50:16 -0500 Received: from smtp116.mail.mud.yahoo.com ([209.191.84.165]:20580 "HELO smtp116.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753011AbZBYDuP (ORCPT ); Tue, 24 Feb 2009 22:50:15 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:X-Yahoo-Newman-Property:From:To:Subject:Date:User-Agent:Cc:References:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding:Content-Disposition:Message-Id; b=u7k0WDrCiM7RsFVufqvZtuRY0tDwUvQLP5/sm3h/yXx0IOvMcuk2doMDzn6IMlt8kP/9fA0qdOPYOj/c9ueTXRXmIvHyolev7+7k1q6aABXw+VWCV93ebYrLvUlkF9LrBCRVCALfX9xDWRKEqTu86vYPJIZOvzvljpAyYnB25g0= ; X-YMail-OSG: .nw1mdUVM1kDMDFE6Nm.qcCRcti8tsNnRbFj8PO01DKpVXW6e2jG_MqNpUGTGqFKKQ5rjStS.TtzMezWjlOzv3wmSKmWNAMNsawlrMRpr4vwGowFzBUR35Nq2NzyOnoHPjs4BhOZUA2kQPuKxeENJfBynpccgSbT55SQIrP7iakujalNquDRc9P5wHO.UNMtgbdX.TonyftBiIrz06bstDScMu1cDQ-- X-Yahoo-Newman-Property: ymail-3 From: Nick Piggin To: Dave Hansen Subject: Re: Another Performance Regression in write() syscall Date: Wed, 25 Feb 2009 14:49:37 +1100 User-Agent: KMail/1.9.51 (KDE/4.0.4; ; ) Cc: Salman Qazi , linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Andi Kleen , Dave Hansen , Linus Torvalds References: <20090224060558.GA14812@google.com> <200902241947.53180.nickpiggin@yahoo.com.au> <1235494732.26788.256.camel@nimitz> In-Reply-To: <1235494732.26788.256.camel@nimitz> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200902251449.38361.nickpiggin@yahoo.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 25 February 2009 03:58:52 Dave Hansen wrote: > On Tue, 2009-02-24 at 19:47 +1100, Nick Piggin wrote: > > On Tuesday 24 February 2009 17:25:45 Dave Hansen wrote: > > > On Mon, 2009-02-23 at 22:05 -0800, Salman Qazi wrote: > > > > Analysis of profile data has led us to believe that the commit > > > > 3d733633a633065729c9e4e254b2e5442c00ef7e has caused a performance > > > > regression. This commit provides for tracking of writers so that > > > > read only bind mounts function correctly. > > > > > > > > We can verify this regression by applying the following patch to > > > > partially disable the above-mentioned commit and then running the > > > > fstime component of Unixbench. The settings used were 256 byte > > > > writes with MAX_BLOCK of 2000. > > > > > > I'm a bit surprised that write() is what is regressing. Unless I > > > screwed up, we do all the expensive accounting at open()/close() time. > > > Is this a test that gets run in parallel on multiple cpus? > > > > Don't forget touch_atime... > > Yeah, that's a good point. Are we sure that's what is happening here, > though? That's one thing a profile would hopefully help with. > > > Still, open/close isn't unimportant either. > > Yeah, that's true. But, what I noticed was that all of the other > open/close activity masked out any overhead from mnt_want/drop_write() > since a big chunk of the overhead was just going and bringing the > vfsmount pieces into the cache. That's very true. > > > Could you take a look at Nick's patches to speed this stuff up? > > > > > > http://thread.gmane.org/gmane.linux.file-systems/28186 > > > > > > We may need to dust those off, although I'm still a bit worried about > > > the complexities of open-coding all the barriers. > > > > I really need to do something about trying to push them upstream again > > actually because we've got them in SLES11 tree. > > Were the patches that you integrated any different from the ones you > posted a few months ago? Don't think they were significantly changed. I'll take another look and repost them.