From: Jacek Luczak Subject: Re: getdents - ext4 vs btrfs performance Date: Sun, 4 Mar 2012 11:25:08 +0100 Message-ID: References: <20120301143859.GX5054@shiny> <20120302140038.GD5054@shiny> <20120302142651.GH5054@shiny> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE To: Chris Mason , Jacek Luczak , Theodore Tso , linux-ext4@vger.kernel.org, linux-fsdevel , LKML , linux-btrfs@vger.kernel.org Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org 2012/3/3 Jacek Luczak : > 2012/3/2 Chris Mason : >> On Fri, Mar 02, 2012 at 03:16:12PM +0100, Jacek Luczak wrote: >>> 2012/3/2 Chris Mason : >>> > On Fri, Mar 02, 2012 at 11:05:56AM +0100, Jacek Luczak wrote: >>> >> >>> >> I've took both on tests. The subject is acp and spd_readdir used= with >>> >> tar, all on ext4: >>> >> 1) acp: http://91.234.146.107/~difrost/seekwatcher/acp_ext4.png >>> >> 2) spd_readdir: http://91.234.146.107/~difrost/seekwatcher/tar_e= xt4_readir.png >>> >> 3) both: http://91.234.146.107/~difrost/seekwatcher/acp_vs_spd_e= xt4.png >>> >> >>> >> The acp looks much better than spd_readdir but directory copy wi= th >>> >> spd_readdir decreased to 52m 39sec (30 min less). >>> > >>> > Do you have stats on how big these files are, and how fragmented = they >>> > are? =A0For acp and spd to give us this, I think something has go= ne wrong >>> > at writeback time (creating individual fragmented files). >>> >>> How big? Which files? >> >> All the files you're reading ;) >> >> filefrag will tell you how many extents each file has, any file with >> more than one extent is interesting. =A0(The ext4 crowd may have bet= ter >> suggestions on measuring fragmentation). >> >> Since you mention this is a compile farm, I'm guessing there are a b= unch >> of .o files created by parallel builds. =A0There are a lot of chance= s for >> delalloc and the kernel writeback code to do the wrong thing here. >> > [Most of files are B and K size] > > All files scanned: 1978149 > Files fragmented: 313 (0.015%) where 11 have 3+ extents > Total size of fragmented files: 7GB (~13% of dir size) BTRFS: Non of files according to filefrag are fragmented - all fit into one extent. > tar cf on fragmented files: > 1) time: 7sec > 2) sw graph: http://91.234.146.107/~difrost/seekwatcher/tar_fragmente= d.png > 3) sw graph with spd_readdir: > http://91.234.146.107/~difrost/seekwatcher/tar_fragmented_spd.png > 4) both on one: > http://91.234.146.107/~difrost/seekwatcher/tar_fragmented_pure_spd.pn= g BTRFS: tar on ext4 fragmented files 1) time: 6sec 2) sw graph: http://91.234.146.107/~difrost/seekwatcher/tar_fragmented_= btrfs.png > tar cf of fragmented files disturbed with [40,50) K files (in total > 4373 files). K files before fragmented M files: > 1) size: 7.2GB > 2) time: 1m 14sec > 3) sw graph: http://91.234.146.107/~difrost/seekwatcher/tar_disturbed= =2Epng > 4) sw graph with spd_readdir: > http://91.234.146.107/~difrost/seekwatcher/tar_disturbed_spd.png > 5) both on one: > http://91.234.146.107/~difrost/seekwatcher/tar_disturbed_pure_spd.png BTRFS: tar on [40,50) K and ext4 fragmented 1) time: 56sec 2) sw graph: http://91.234.146.107/~difrost/seekwatcher/tar_disturbed_b= trfs.png New test I've included - randomly selected files: - size 240MB 1) ext4 (time: 34sec) sw graph: http://91.234.146.107/~difrost/seekwatcher/tar_random_ext4.png 2) btrfs (time: 55sec) sw graph: http://91.234.146.107/~difrost/seekwatcher/tar_random_btrfs.png -Jacek