In-Reply-To: <[email protected]>
On Sat, 01 Jul 2006 21:42:22 +0200, Arjan van de Ven wrote:
> > What sort of test?
>
> the one I did was long running FPU app (calculating PI using FPU)
Mine was just running a program that loops doing getpid() in one window
and this in another:
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#define rdtscll(t) asm("rdtsc" : "=A" (t))
int main(int argc, char * const argv[])
{
long long tsc1, tsc2;
long double ld = 0.0;
int i, iters = 999999999;
rdtscll(tsc1);
for (i = 0; i < iters; i++)
ld += 1.0;
rdtscll(tsc2);
printf("count: %Lf, clocks: %llu\n", ld, tsc2 - tsc1);
return 0;
}
So the ~0.4% gain I saw (averaging 10 tests) was likely the minimum
and Arjan's 8.5% gain when switching tasks after every FPU operation
is the max.
--
Chuck
"You can't read a newspaper if you can't read." --George W. Bush
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