Re: test time-warps [was: Re: 2.6.14-rt13]

From: Ingo Molnar
Date: Tue Nov 22 2005 - 15:52:18 EST

* Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> > > Apparently that's the case.
> >
> > What about periodically re-syncing the TSCs on the cpus? Are they
> > writeable?
> I believe you can reset them to zero, but I don't think you can set
> them to anything else. I had to do something similar a few years ago,
> and I don't have the specs in front of me, so this is coming straight
> from memory.

on a reasonably new CPU you ought to be able to set the 64-bit value -
but that doesnt change the fundamental fact: we have no idea how much
time has passed while we were in HLT. Especially with things like
dyntick/noidle we could spend _alot_ of time in HLT, and the TSC could
drift significantly. How do we know how much that is?

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