Messages in this thread | | | Date | Wed, 30 Apr 1997 14:31:35 +0200 (MET DST) | From | Ingo Molnar <> | Subject | Re: Utilizing rdtsc on i586? |
| |
On Wed, 30 Apr 1997, Harald Koenig wrote:
[...] > it's not necessary to run this in kernel; using user mode is ok too: >
plus the following is handy too:
> void main(void) > { > unsigned int cnt3, cnt2, cnt1; > int i; > printf("cc: started... ");
iopl(3); __asm__("cli");
> __asm__(".byte 0x0f,0x31" : "=a" (cnt1), "=d" (cnt3)); > /* put code to time here */ > for(i=0;i<10000;i++); > /* end code to time here */ > __asm__(".byte 0x0f,0x31" : "=a" (cnt2), "=d" (cnt3));
__asm__("sti");
> printf(" operation took %d cycles\n", cnt2-cnt1); > }
you've got to run it as root, and better make no mistakes between cli and sti ;)
-- mingo
| |