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

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 25/1/08 17:19, "Stephen C. Tweedie" <sct@xxxxxxxxxx> wrote:

>> 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.
> 
> They are most definitely serious --- gettimeofday() going backwards
> breaks Unix semantics.  It breaks applications.  It _will_ corrupt
> application data --- things like database rollback logs that rely on
> timestamp monotonicity to order things correctly will break.
> 
> I think this is something that Xen upstream ought to be pretty concerned
> about.  If we can't fix it properly, then the workaround of disabling
> powernow seems to be a must-have.

It's a primary reason why we hide it behind an explicit Xen boot parameter.

 -- Keir



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