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

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 23/1/08 15:17, "Langsdorf, Mark" <mark.langsdorf@xxxxxxx> wrote:

>> Yes, and that is already done, hooked off the cpu notifier
>> callback chain.
>> Nobbling the C- and P-state logic shouldn't be necessary.
> 
> And yet, people are still reporting "Time went backwards"
> messages upwards of 30-40 times an hour on RevF Opterons
> when PowerNow! is enabled on Xen.
> 
> I spent a month trying to debug this and I made no significant
> progress.  If someone who understands Xen timekeeping wants to
> help me dive into this, I'll be glad to take another stab at
> it.  As it is, even with informing Xen of frequency changes,
> Xen does not ensure monotinicity.

Seeing them at that frequency (less than one a minute) is not too serious.
Perhaps we should get rid of the message, or reduce its priority.

 -- Keir



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