Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759865Ab1CDPul (ORCPT ); Fri, 4 Mar 2011 10:50:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:28161 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759804Ab1CDPuk (ORCPT ); Fri, 4 Mar 2011 10:50:40 -0500 From: Jeff Moyer To: Jan Kara Cc: Corrado Zoccolo , "Alex\,Shi" , "Li\, Shaohua" , Vivek Goyal , "tytso\@mit.edu" , "jaxboe\@fusionio.com" , "linux-kernel\@vger.kernel.org" , "Chen\, Tim C" Subject: Re: [performance bug] kernel building regression on 64 LCPUs machine References: <1297732201.24560.2.camel@sli10-conroe> <20110221164909.GG6584@quack.suse.cz> <1298449487.14712.1064.camel@debian> <20110224121339.GE23042@quack.suse.cz> <20110302094246.GA7496@quack.suse.cz> <20110302211748.GF7496@quack.suse.cz> <20110304153248.GC2649@quack.suse.cz> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Fri, 04 Mar 2011 10:50:32 -0500 In-Reply-To: <20110304153248.GC2649@quack.suse.cz> (Jan Kara's message of "Fri, 4 Mar 2011 16:32:48 +0100") Message-ID: User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1317 Lines: 29 Jan Kara writes: > I'm not so happy with ext4 results. The difference between ext3 and ext4 > might be that amount of data written by kjournald in ext3 is considerably > larger if it ends up pushing out data (because of data=ordered mode) as > well. With ext4, all data are written by filemap_fdatawrite() from fsync > because of delayed allocation. And thus maybe for ext4 WRITE_SYNC_PLUG > is hurting us with your fast storage and small amount of written data? With > WRITE_SYNC, data would be already on it's way to storage before we get to > wait for them... > Or it could be that we really send more data in WRITE mode rather than in > WRITE_SYNC mode with the patch on ext4 (that should be verifiable with > blktrace). But I wonder how that could happen... It looks like this is the case, the I/O isn't coming down as synchronous. I'm seeing a lot of writes, very few write sync's, which means that the write stream will be preempted by the incoming reads. Time to audit that fsync path and make sure it's marked properly, I guess. Cheers, Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/