From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans Reiser Subject: Re: Desktop Filesystem Benchmarks in 2.6.3 Date: Wed, 03 Mar 2004 09:30:54 +0300 Message-ID: <40457B9E.3060706@namesys.com> References: <4044119D.6050502@andrew.cmu.edu> <4044366B.3000405@namesys.com> <4044B787.7080301@andrew.cmu.edu> <1078266793.8582.24.camel@mentor.gurulabs.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com In-Reply-To: <1078266793.8582.24.camel@mentor.gurulabs.com> List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Dax Kelson Cc: Peter Nelson , linux-kernel , ext2-devel@lists.sourceforge.net, ext3-users@redhat.com, jfs-discussion@oss.software.ibm.com, reiserfs-list@namesys.com, linux-xfs@oss.sgi.com Unfortunately it is a bit more complex, and the truth is less complementary to us than what you write. Reiser4's CPU usage has come down a lot, but it still consumes more CPU than V3. It should consume less, and Zam is currently working on making writes more CPU efficient. As soon as I get funding from somewhere and can stop worrying about money, I will do a complete code review, and CPU usage will go way down. There are always lots of stupid little things that consume a lot of CPU that I find whenever I stop chasing money and review code. We are shipping because CPU usage is not as important as IO efficiency for a filesystem, and while Reiser4 is not as fast as it will be in 3-6 months, it is faster than anything else available so it should be shipped. Hans Dax Kelson wrote: >On Tue, 2004-03-02 at 09:34, Peter Nelson wrote: > > >>Hans Reiser wrote: >> >>I'm confused as to why performing a benchmark out of cache as opposed to >>on disk would hurt performance? >> >> > >My understanding (which could be completely wrong) is that reieserfs v3 >and v4 are algorithmically more complex than ext2 or ext3. Reiserfs >spends more CPU time to make the eventual ondisk operations more >efficient/faster. > >When operating purely or mostly out of ram, the higher CPU utilization >of reiserfs hurts performance compared to ext2 and ext3. > >When your system I/O utilization exceeds cache size and your disks >starting getting busy, the CPU time previously invested by reiserfs pays >big dividends and provides large performance gains versus more >simplistic filesystems. > >In other words, the CPU penalty paid by reiserfs v3/v4 is more than made >up for by the resultant more efficient disk operations. Reiserfs trades >CPU for disk performance. > >In a nutshell, if you have more memory than you know what do to with, >stick with ext3. If you spend all your time waiting for disk operations >to complete, go with reiserfs. > >Dax Kelson >Guru Labs > > > > > -- Hans