On Tue, 2007-11-20 at 19:27 +0300, Alexey Popov wrote: > Hi. > <snip> > After that I rebuilt with SMP GENERIC kernel and put on that server 2 > times more requests that UP could handle. For the first time it worked > good. Then I increased load to 2.5 times more than UP. Immediately > Apache child count increased to MaxClients (24), most of them in RUN > state, and %sys became greater than %user (see attach). I think after > some threshold of load FreeBSD is paying more CPU time to the management > of running processes than to run them. > > Also I tried to halt CPUs by machdep.hlt_cpus sysctl, but in that case > %sys in top was still much greater than %user.
MaxClients of 24 seems very low for a 8 cpu box, running prefork MPM. On our quad CPU boxes, running custom apache modules, we use MaxClients 70 MinSpareServers 5 MaxSpareServers 15 StartServers 20 Perhaps you are seeing high system load because the system is having to maintain a lot of queued connections. Certainly, our load remains in-between comfortable margins, except when heavily stressed. Tom
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