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Date: Wed, 13 Jan 2016 05:36:30 +1100 (EST)
From: Ian Smith <smithi@nimnet.asn.au>
To: kpneal@pobox.com
cc: "William A. Mahaffey III" <wam@hiwaay.net>, freebsd-questions@freebsd.org
Subject: Re:  Task to busy one CPU 100% for a period of time?
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On Mon, 11 Jan 2016 15:38:32 -0500, kpneal@pobox.com wrote:
 > On Mon, Jan 11, 2016 at 04:04:05PM +1100, Ian Smith wrote:
 > > Thanks for your response.  However I don't do C, and really need to find
 > > something out of the box that I can configure to run at 100% of one CPU 
 > > for a specified number of iterations, which will then run for a certain 
 > > amount of CPU time on my hardware, while always on the run queue.
 > 
 > Won't this reproduce your results? 
 > 
 > Two compilations: 
 > 
 > /* main.c */
 > int main() {
 >    for (;;)
 >       dummy_function();
 >    /*NOTREACHED*/
 >    return(0);
 > }
 > 
 > /* dummy.c */
 > int dummy_function(void) {
 >    return 0;
 > }
 > 
 > cc -c main.c
 > cc -c dummy.c
 > cc -o load1 main.o dummy.o
 > 
 > One invocation of this program should consume an entire CPU and therefore
 > raise the load average by 1.00. Run as many as you like.
 > 
 > (The reason for the two compilations is to avoid having any compiler
 > optimize away the for loop. Just to be safe.)

Thankyou Kevin.  Works a treat, so far tested 8 at once, loadavg = 8.00

I'll follow up hopefully tomorrow with results of a sh script to run a 
given number of instances for a given time, needing a bit more testing.

cheers, Ian