FreeBSD MySQL still WAY slower than Linux

[Billy Newsom]

Steve Roome wrote:
 > We're using mostly:
 >
 >   5.4-STABLE FreeBSD 5.4-STABLE #0: Mon Jun 6 12:22:18 BST 2005
 >
 > This is on a Dell PowerEdge 2850. (2 * 2.8 GHz Xeons, 4GB ram, disks),
 > we've been keeping up with stable because supposedly all these new
 > fixes to threading will help us out here.
 >
 > We're trying to get FreeBSD to perform reasonably well, in comparison
 > to Linux, or even what we should expect to see. We're getting about
 > half the performance we get from gentoo on the same application
 > (mysql).
 >
[snip]

 > Thanks in advance for anyone that has a clue on this, and has anyone
 > figured out why FreeBSD is just so amazingly slow compared to Linux.
 >

Have you looked around for different compilers and/or different compiler 
options?  I was just remembering how different code can be, depending on 
which gcc, for example, was used, and definitely which optimization. 
(i.e. Try "gcc -v" on both systems to see if they match; next see if all 
compiler options match when they are compiling like -march=pentiumpro.) 
  Meanwhile, I have heard good things about compiler "fill in the blank" 
for whatever.  Not too long ago, I remember hearing about people who 
preferred to use, say, an Intel compiler for certain things.  It might 
be interesting to see if FreeBSD 4.11 is just as slow as 5.x.  And try 
feeding the right compiler flags using /etc/make.conf or its equivalent.

You should also think about whether the file systems are mounted using 
similar, or equally-performing systems.  Rumour has it that Linux file 
systems performance is .... [flame bait mysteriously deleted]...  Your 
benchmark may produce some interesting results, for example, depending 
on whether it thrashes a disk, or mainly hits memory.  Do they perform 
the same on small sized (cached) lookups and then FreeBSD bogs down on 
disk throughput, for example?

Last, but not least, I have heard some not-so-impressive things about 
MySQL 4.1 when compared to 4.0.  Perhaps the things I heard were in 
reality specific to FreeBSD, and so by dropping back to 4.0 on a test 
server, you might see an unexpected performance boost?  (Be sure and 
delete the tables between runs.)  4.0 is still in the ports tree, and I 
have heard of some who wished they never upgraded to 4.1.  But going 
backwards is not pretty for a live database, so test both versions now.

Billy