Re: Intel P6 vs P7 system call performance
H. Peter Anvin (email@example.com)
Thu, 19 Dec 2002 14:23:26 -0800
Pavel Machek wrote:
>>>>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.
Backwards?? Clock spreading should make the rate change, but it should
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