From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Sun, 16 Jul 2006 08:52:21 -0700 (PDT) Received: from larry.melbourne.sgi.com (larry.melbourne.sgi.com [134.14.52.130]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with SMTP id k6GFpaDW008577 for ; Sun, 16 Jul 2006 08:51:48 -0700 Date: Mon, 17 Jul 2006 01:50:29 +1000 From: David Chinner Subject: Re: Bonnie getc reading hitting exact 65536 kb/s Message-ID: <20060716155029.GR15160733@melbourne.sgi.com> References: <20060715171304.59053A00A8A@smtp.funpic.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060715171304.59053A00A8A@smtp.funpic.de> Sender: xfs-bounce@oss.sgi.com Errors-To: xfs-bounce@oss.sgi.com List-Id: xfs To: "A. Liemen" Cc: xfs@oss.sgi.com On Sat, Jul 15, 2006 at 07:13:10PM +0200, A. Liemen wrote: > Hi, > > during some xfs tuning tests I discovered the following phenomenon. > Maybe someone can explain it to me: > > Bonnie++ Reading with getc()... hits exactly an almost constant > 65536 kbyte/s with only ~15% IO usage. > > iostat and bonnie output can be found under: > > http://alexander.liemen.net/bonnie.txt Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP storage4 40000M 64890 99 229195 39 105826 24 63895 98 350285 38 361.1 0 ^^^^^^^^^ ^^^^^^^^^ It's cpu bound, not I/O bound. It can't go any faster because it's a single threaded test.... > CPU usage is 100% (on one of the cpus) but i don't think that's the > limiting factor since it hits that 16bit value absolut constantly. What you are seeing is XFS issuing regular sized I/Os at a constant throughput. If you really think this is a 16bit ceiling, see what the block I/O tests report in iostat - you're getting ~230MB/s for write and 350MB/s for read, so if iostat is has a bug then you'll see it there. > Also of interest would be why the random seeks are so bad. Try creating more than 16 files for youre create/read/delete so that the runtime is somewhat greater than the timer resolution.... Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group