RE: [Xen-devel] [PATCH] Disable Xen PowerNow! support on Opteron 2nd gen and earlier processors

["Langsdorf, Mark" <mark.langsdorf@xxxxxxx>]

> > I tried this suggestion and also implemented the trace function in
> > cpu_frequency_change() and local_time_calibration() you 
> > suggested in a previous message.
> 
> Please provide the output of the tracing.

I did, in the attached gzip'd xm dmesg log.

> Presumably the time-goes-backwards messages only come out when
> stepping frequency down?

The time-goes-backwards messages appear in Xen when 
stepping frequency down, and when the frequency goes up.

> Presumably it is the CPU that is down-stepping that thinks 
> time has gone backwards?

> The messages comes out shortly after the downstep?

Yes, but the Xen trace
 
> Once the multiplier change has happened, you need to create a new time
> record for the CPU based on the global clock PIT/HPET (and update the
> frequency info in the record).

I thought I was doing that already.  The code that is in
there now was written on Keir based on my original design.
 
> Implemented correctly, this really ought to work just fine.

We seem to be missing something in the correct implementation.

-Mark Langsdorf
Operating System Research Center
AMD



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