Re: Intel P6 vs P7 system call performance

Pavel Machek (pavel@ucw.cz)
Thu, 19 Dec 2002 23:21:36 +0100


Hi!

> >>don't many of the multi-CPU problems with tsc go away because you've got a
> >>per-cpu physical page for the vsyscall?
> >>
> >>i.e. per-cpu tsc epoch and scaling can be set on that page.
> >
> > Problem is that cpu's can randomly drift +/- 100 clocks or so... Not
> > nice at all.
> >
>
> ญญ?100 clocks is what... ?50 ns these days? You can't get that kind of
> accuracy for anything outside the CPU core anyway...

50ns is bad enough when it makes your time go backwards.

Pavel

-- 
Casualities in World Trade Center: ~3k dead inside the building,
cryptography in U.S.A. and free speech in Czech Republic.
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