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

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

> >> 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.

Red Hat engineering is requesting the disable because they've
gotten STREAM results with the test finishing before it started.

For myself, I don't mind the frequency of the messages.  In the
real world, it's serious, especially on financial servers.

-Mark Langsdorf
Operating System Research Center
AMD



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel