Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030762Ab2B2NwH (ORCPT ); Wed, 29 Feb 2012 08:52:07 -0500 Received: from acsinet15.oracle.com ([141.146.126.227]:20908 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758002Ab2B2NwF (ORCPT ); Wed, 29 Feb 2012 08:52:05 -0500 Date: Wed, 29 Feb 2012 08:51:58 -0500 From: Chris Mason To: Jacek Luczak Cc: linux-ext4@vger.kernel.org, linux-fsdevel , LKML , linux-btrfs@vger.kernel.org, Al Viro , "Ted Ts'o" Subject: Re: getdents - ext4 vs btrfs performance Message-ID: <20120229135158.GA5054@shiny> Mail-Followup-To: Chris Mason , Jacek Luczak , linux-ext4@vger.kernel.org, linux-fsdevel , LKML , linux-btrfs@vger.kernel.org, Al Viro , Ted Ts'o References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: acsinet22.oracle.com [141.146.126.238] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090201.4F4E2D81.01A4,ss=1,re=0.000,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2766 Lines: 69 On Wed, Feb 29, 2012 at 02:31:03PM +0100, Jacek Luczak wrote: > Hi All, > > Long story short: We've found that operations on a directory structure > holding many dirs takes ages on ext4. > > The Question: Why there's that huge difference in ext4 and btrfs? See > below test results for real values. > > Background: I had to backup a Jenkins directory holding workspace for > few projects which were co from svn (implies lot of extra .svn dirs). > The copy takes lot of time (at least more than I've expected) and > process was mostly in D (disk sleep). I've dig more and done some > extra test to see if this is not a regression on block/fs site. To > isolate the issue I've also performed same tests on btrfs. > > Test environment configuration: > 1) HW: HP ProLiant BL460 G6, 48 GB of memory, 2x 6 core Intel X5670 HT > enabled, Smart Array P410i, RAID 1 on top of 2x 10K RPM SAS HDDs. > 2) Kernels: All tests were done on following kernels: > - 2.6.39.4-3 -- the build ID (3) is used here for internal tacking of > config changes mostly. In -3 we've introduced ,,fix readahead pipeline > break caused by block plug'' patch. Otherwise it's pure 2.6.39.4. > - 3.2.7 -- latest kernel at the time of testing (3.2.8 has been > release recently). > 3) A subject of tests, directory holding: > - 54GB of data (measured on ext4) > - 1978149 files > - 844008 directories > 4) Mount options: > - ext4 -- errors=remount-ro,noatime,data=writeback > - btrfs -- noatime,nodatacow and for later investigation on > copression effect: noatime,nodatacow,compress=lzo For btrfs, nodatacow and compression don't really mix. The compression will just override it. (Just FYI, not really related to these results). > > In all tests I've been measuring time of execution. Following tests > were performed: > - find . -type d > - find . -type f > - cp -a > - rm -rf > > Ext4 results: > | Type | 2.6.39.4-3 | 3.2.7 > | Dir cnt | 17m 40sec | 11m 20sec > | File cnt | 17m 36sec | 11m 22sec > | Copy | 1h 28m | 1h 27m > | Remove| 3m 43sec Are the btrfs numbers missing? ;) In order for btrfs to be faster for cp -a, the files probably didn't change much since creation. Btrfs maintains extra directory indexes that help in sequential backup scans, but this usually means slower delete performance. But, how exactly did you benchmark it? If you compare a fresh mkfs.btrfs where you just copied all the data over with an ext4 FS that has been on the disk for a long time, it isn't quite fair to ext4. -chris -- 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/