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

[John Levon <levon@xxxxxxxxxxxxxxxxx>]

On Fri, Jan 25, 2008 at 05:19:53PM +0000, Stephen C. Tweedie 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 thought Linux now enforced a monotonic clock the same way we were
forced to - that is, globally synchronise and make sure we return last
value + 1, even when the Xen clock goes backwards across CPUs, which it
does regularly, powernow or not?

regards
john

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