Messages in this thread | | | Date | Thu, 19 Dec 2002 14:23:26 -0800 | From | "H. Peter Anvin" <> | Subject | Re: Intel P6 vs P7 system call performance |
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Pavel Machek wrote: > 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. >>> >> >>?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. >
Backwards?? Clock spreading should make the rate change, but it should never decrement.
-hpa
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