Re: MySQL benchmarks

On Wed, 2005-02-09 at 15:37 -0700, Scott Long wrote:
> Miguel Mendez wrote:
> 
> > Hi all,
> > 
> > Someone has posted a link to a newsforge article on the NetBSD lists
> > that benchmarks MySQL performance on several systems, you can see it at:
> > 
> > http://software.newsforge.com/article.pl?sid=04/12/27/1243207&from=rss
> > 
> > I don't know how much Linux-specific code there is in MySQL because,
> > honestly, I always try to avoid it and go with PostgreSQL, but perhaps
> > somebody with more MySQL-fu can fill in the blanks and confirm that the
> > better performance seen on Linux systems is due to how the software is
> > designed and not so much related to FreeBSD per se.
> > 
> > Cheers,
> 
> There has long been speculation that Linux cuts corners on these tests
> by ignoring things like fsync.  One thing that I've been meaning to do
> for a while is to ktrace some of the mysql benchmarks and see what
> exactly is going on, then compare that to a similar ktrace run under
> Linux.  If it turns out that there are lots of synchronization calls
> (i.e. fsync-like calls), try stubbing them out in FreeBSD and see if it
> brings you any closer to the linux scores.
> 
> An easier but also informative test would be to remount the database
> filesystem as async-noatime-nosoftupdates and see how it compares.

The test was performed using Innodb... and if the define is available,
it usually opens its filestore with the O_DIRECT flag. Also, expect
plenty of fsync() calls. If Linux is returning from the write() calls
without pushing the data to disk, that itself will give it a sizable
lead.

If I remember correctly, MyISAM with skip-locking should rarely use
fsync() calls... so if possible, the test could be re-run using MyISAM
tables to see if there is any performance difference.

I have not personally done any performance comparisons between FreeBSD
and Linux in more than a year but the last time I compared FreeBSD 5
pthreads and Linux, Linux does appear to have the edge on thread
creation and synchronisation. However, I have switched all my machines
to be running FreeBSD since... (rpm hell experience during upgrading)

YMMV, opinions are mine and not my employer, yadda yadda yadda...

-- 
Antony T Curtis, BSc.                   UNIX, Linux, *BSD, Networking
antony.t.curtis_at_ntlworld.com            C++, J2EE, Perl, MySQL, Apache
                                        IT Consultancy.