Adrian Bunk wrote: {
On Tue, Jul 26, 2005 at 08:22:59AM +0300, Al Boldi wrote:
> Dr. Horst H. von Brand wrote: {
> Al Boldi <[email protected]> wrote:
> > Adrian Bunk wrote: {
> > On Fri, Jul 22, 2005 at 07:55:48PM +0100, christos gentsis wrote:
> > > i would like to ask if it possible to change the optimization of the
> > > kernel from -O2 to -O3 :D, how can i do that? if i change it to the
> > > top level Makefile does it change to all the Makefiles?
> > And since it's larger, it's also slower.
> > }
>
> > It's faster but it's flawed. Root-NFS boot failed!
>
> How do you know that it is faster if it is busted?
> }
>
> The -O3 compile produces a faster kernel, which seems to work perfectly,
> albeit the Root-NFS boot flaw!
How did you measure that you that your -O3 kernel isn't slower?
}
Gettimeofday loops using gcc-3.2.2 on 2.4.31 and 2.6.12.
Also, 2.4 is faster than 2.6!
Try this:
#define __USE_GNU
#include <stdio.h>
#include <sys/time.h>
unsigned long elapsed(int start) {
static struct timeval s,e;
if (start) return gettimeofday(&s, NULL);
gettimeofday(&e, NULL);
return ((e.tv_sec - s.tv_sec) * 1000 + (e.tv_usec - s.tv_usec) /
1000);
}
int main(int argc, char *argv[]) {
int i;
elapsed(1);
for (i = 0; elapsed(0) < 100; i++) {
int ret = i;
if (ret > i)
break;
else if (ret < 0) {
perror("not here");
break;
}
ret++;
}
printf("Elapsed: %lu in %lums %lu/ms",i,elapsed(0),i/elapsed(0));
int tmo=i;
elapsed(1);
for (i = 0; i < 100*tmo ; i++) {
int ret = i;
if (ret > i)
break;
else if (ret < 0) {
perror("not here");
break;
}
ret++;
}
printf(" - %lu/ms",i/elapsed(0));
elapsed(1);
for (i = 0; i < 100*tmo ; i++);
printf(" - %lu/ms\n",i/elapsed(0));
return 0;
}
--
Al
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