lightly loaded php+mysql - high syscall/csw rates

Frank Shute frank at
Thu Nov 22 11:59:32 PST 2007

On Thu, Nov 22, 2007 at 12:43:25PM +0300, 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.

Andrew, I don't know if you've been following stable@ but there is a
long thread there about php performance (amongst other things).


"2 x quad-core system is slower that 2 x dual core on FreeBSD"[sic]

Apologies, if it's not related to the problem you're seeing. (It's
over my head).



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