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SubjectRe: TSC Problems (warp between CPUs)
On 2013-12-29 01:35, One Thousand Gnomes wrote:
>> not guaranteed to be precise. For example a SMI (System Management
>> Interrupt) could interrupt the software flow that is attempting to
>> write
>> the time-stamp counter immediately prior to the WRMSR. This could
>> mean
>> the value written to the TSC could vary by thousands to millions of
>> clocks.
>
> Yes SMI is a disaster area for any real time activity (and many other
> things ;) ), but many systems actually make little use of it,
> especially
> once the USB is owned by the OS.
>
> For synchronization you can retry the sync if it isn't within an
> acceptable range. The odds of getting an SMI mid sync setup should be
> very very low, so the odds of repeating the failure several times
> should
> be negligible and after a few tries you could give up and assume the
> hardware is buggered then fall back to HPET.

Hi Alan,

The sync retry sounds like an interesting strategy but is outside my
knowledge
scope as a regular end user (I do have a reasonable understanding of C
and can patch+
recompile) but I lack the architecture knowledge to implement a patch
to do this.

Any suggestions?

--
Kind Regards,
Alex.



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