Re: Intel P6 vs P7 system call performance

GrandMasterLee
2002-12-17T06:11:11Z

On Tue, 2002-12-17 at 00:09, Linus Torvalds wrote:
> On Mon, 16 Dec 2002, Linus Torvalds wrote:
> >
> > On my P4 machine, a "getppid()" is 641 cycles with sysenter/sysexit, and
> > something like 1761 cycles with the old "int 0x80/iret" approach. That's a
> > noticeable improvement, but I have to say that I'm a bit disappointed in
> > the P4 still, it shouldn't be even that much.
>
> On a slightly more real system call (gettimeofday - which actually matters
> in real life) the difference is still visible, but less so - because the
> system call itself takes more of the time, and the kernel entry overhead
> is thus not as clear.
>
> 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.

I'm curious, if this is one of the Dual P4's non-Xeon(say, 2.4 Ghz+?) or
if this is one of the Xeons? There seems to be some perceived disparity
between which performs how. I think the biggest difference on the Xeon's
is the stepping and the cache,(pipeline too?), but not too much else.

[...]
> Linus
>