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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. User on cpu1 reads time, communicates it to cpu2, but cpu2 is drifted -50ns, so it reads time "before" time reported cpu1. And gets confused. Pavel -- Casualities in World Trade Center: ~3k dead inside the building, cryptography in U.S.A. and free speech in Czech Republic. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
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