lightly loaded php+mysql - high syscall/csw rates

[Andrew Pantyukhin]

On Thu, Nov 22, 2007 at 02:52:06PM +0000, Vince wrote:
> Andrew Pantyukhin wrote:
> > We have a php+mysql web server. It serves 15-20 http requests per
> > second, resulting in 100-200 sql qps. But according to vmstat(1),
> > it all peaks at over 500k syscall/s and 100k cswitch/s. The peaks
> > are quite frequent, even at this load. During the peaks top(1)
> > shows 30-40k VCSW for mysql and around 1k vcsw for two php-cgi
> > worker processes. IVCSW is relatively very low for all processes.
> > 
> > This is a 4-core Opteron HP DL145 G2 server running 6.2/amd64
> > generic+quota. I'm considering a switch to 7.0.
> > 
> > During peaks user/system/idle in top(1) is 20/30/50.
> > 
> > The question is - is the syscall and csw rates normal or should I
> > be trying to tune mysql and php more agressively? I'm not hungry
> > for performance (haven't hit the limit yet), but a couple of days
> > ago the server stopped responding until a cold reboot (which is
> > another story) - and now I'm paying closer attention to its
> > vitals.
> This sounds like it could be related to the issues being discussed on a
> thread on freebsd-stable titled "2 x quad-core system is slower that 2 x
> dual core on FreeBSD"
> [http://docs.freebsd.org/cgi/mailindex.cgi?sort=subject&file=current/freebsd-stable]

Yeah, I'm following that thread, I just wanted to know if anyone
else gets 500k+ syscalls per second on an php+mysql web server
at 20 pages per second.