Re: [ck] Re: [announce] [patch] Voluntary Kernel Preemption Patch

[Ingo Molnar]

* Chris Friesen <cfriesen@xxxxxxxxxxxxxxxxxx> wrote:

> >it was reporting more accurate latencies, except that there were strange
> >spikes of latencies. It turned out that for whatever reason, userspace
> >RDTSC is not always reliable on my box (!).
> 
> Would the fact that rdtsc is not serializing have any effect here?  Or
> would that be a small enough error to not have any effect?

even though it's not serializing (to other instructions), one would
expect the '64-bit cycle counter' to be fetched atomically. And several
milliseconds cannot be explained with any micr-op delays anyway.

	Ingo
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