Suns on their knees

[Joel Clark]

_____________________________________________________________________
 weiser.pa at xerox.com writes:
>#include <sys/time.h>
>
>main()
>  {
>  struct timeval tv;
>
>  tv.tv_sec = 0;
>  tv.tv_usec = 100000;
>  for( ;; )
>    select( 0, 0, 0, 0, &tv );
>  }
>
> I changed 100000 to 25000, and ran 18 of these on my
> Sun-4/260 with 120MB swap and 24MB ram, with very little else going on.
> Perfmeter shows no disk activity, ps aux shows each of the 18 using almost no
> cpu. Each of the 18 has more than millisecond to get in and out of select,
> which is certainly enough.  And the system is to its knees!  If it doesn't
> work for you, try 19 or 20 or 21. Window refreshes take 10's of seconds. If I
> kill off 3 of these, all is back to normal.
> 
> I don't have a 60C to try this on. But, try reducing that delay factor and see
> if you also see a knee in the performance curve well before the cpu should
> be swamped.  (And in any case, swamped cpu doesn't need to imply knee in the
> curve...)

> -mark
> 

Some  people wanted to know if the Knee showed up in a Sun 386i Road Runner.
I tried this program yesterday with 100000 changed to 25000.  Performance
drops off the edge of usefulness at about 20 processes.


Joel Clark
Intel Scientific Computers			joel at intelisc.UUCP.COM
Beaverton, Oregon 97201			{tektronix}!ogcvax!intelisc!joel
(503) 629-7732