2 x quad-core system is slower that 2 x dual core on FreeBSD

[Robert Watson]

On Mon, 19 Nov 2007, Alexey Popov wrote:

> I tried Linux and it works much better than old (2 x dual-core) backends. It 
> handles 2 times more requests than FreeBSD on the old backends. So there's a 
> real scalability problem in FreeBSD. The more processors it have the more 
> CPU time it consumes.
>
> Also I faced the same problem moving heavily loaded MySQL-server to new 
> hardware. That time I thought that the problem is in the mysql-server itself 
> and I had to install Linux.
>
> See in attach: mutex statistics for quad-core system and dmesg and vmstat 
> for dual- and quad-core systems.
>
> What can I do to make FreeBSD run faster on many-CPU systems???

Have you configured libmap.conf to force MySQL to use libthr instead of 
libpthread?  libpthread is known to have serious performance bottlenecks for 
MySQL as compared to libthr.

FreeBSD 7 contains significant optimization for increased numbers of cores, 
and is where a lot of the work optimizing MySQL has ended up.  I see you're 
trying out a 6.3 beta, any chance you could try out a 7.0 beta instead? 
Also, consider switching to "options SCHED_ULE" in the 7.0 kernel rather than 
"options SCHED_4BSD".

Robert N M Watson
Computer Laboratory
University of Cambridge