Re: Intel P6 vs P7 system call performance

Linus Torvalds
2002-12-17T06:09:39Z

On Mon, 16 Dec 2002, Linus Torvalds wrote:
>
> For gettimeofday(), the results on my P4 are:
>
> sysenter: 1280.425844 cycles
> int/iret: 2415.698224 cycles
> 1135.272380 cycles diff
> factor 1.886637
>
> ie sysenter makes that system call almost twice as fast.

Final comparison for the evening: a PIII looks very different, since the
system call overhead is much smaller to begin with. On a PIII, the above
ends up looking like

gettimeofday() testing:
sysenter: 561.697236 cycles
int/iret: 686.170463 cycles
124.473227 cycles diff
factor 1.221602

ie the speedup is much less because the original int/iret numbers aren't
nearly as embarrassing as the P4 ones. It's still a win, though.

Linus