2 x quad-core system is slower that 2 x dual core on FreeBSD
rwatson at FreeBSD.org
Mon Nov 19 06:02:48 PST 2007
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
Robert N M Watson
University of Cambridge
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