Re: Progress on scaling of FreeBSD on 8 CPU systems

On Mon, Feb 26, 2007 at 07:08:37PM +1100, Peter Jeremy wrote:
> On 2007-Feb-24 16:31:11 -0500, Kris Kennaway <kris_at_obsecurity.org> wrote:
> >We have recently made significant progress on optimizing for MySQL
> >running on an 8-core amd64 system. The graph of results may be found
> >here:
> >
> >  http://www.freebsd.org/~kris/scaling/scaling.png
> 
> Those results look wonderful.  Have you tried increasing the number of
> threads to see if there's any nasty knee further to the right?  Also,
> is there any chance of repeating this testing on one of the big Suns
> (or a T2000) to see how this scales to lots of cores?

I didnt try at much higher loads yet, that will be interesting to
explore.

Currently on the Sun T2000 (32 hardware threads = virtual CPUs) we
don't have good scaling (it's hard even to saturate all CPUs for
kernel workloads): the current thinking is that this is largely
because of contention on the global scheduler lock.  Even when idle
there is a lot of contention on the sched_lock coming from e.g. all 32
CPUs running statclock at once HZ=1000 times a second and fighting for
the sched_lock.

Fixing this is something Jeff and Attilio are working on (Kip Macy
also did a lot of exploratory work last year), so we hope to make
further progress over the coming weeks.

Kris