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

Ingo Molnar
2004-07-12T14:19:09Z

* Chris Friesen <cfriesen@nortelnetworks.com> 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