Behavior difference between xen and non-xen kernel

Konstantin Svist fry.kun at
Thu Jun 21 21:28:41 UTC 2007

I've seen this in FC6 and tracked it down to some old posts that 
basically say that xen does not (fully) support power saving features.

 From what I understand, the system clock is based on counting CPU
cycles (when the computer is running, of course) - and frequency scaling 
changes the frequency, thereby making it harder to keep the clock in 
sync. With xen, there is more than one OS running on the CPU - and 
keeping it all in sync becomes really hard.

Not sure why it won't power off after shutdown, though...

Aaron Konstam wrote:
> The difference between the behavior of the xen and non-xen kernel in F7
> on my laptop is puzzling. In grub.conf I have the lines:
> title Fedora (2.6.20-2925.11.fc7xen)
>         root (hd0,2)
>         kernel /boot/xen.gz-2.6.20-2925.11.fc7
>         module /boot/vmlinuz-2.6.20-2925.11.fc7xen ro root=LABEL=/ rhgb
> quiet
>         module /boot/initrd-2.6.20-2925.11.fc7xen.img
> Booting this kernel indicates that cpu scaling is not supported and the
> machine does not shut off when I do a shut down.
> The lines for the non-xen kernel:
> title Fedora (2.6.21-1.3228.fc7)
>         root (hd0,2)
>         kernel /boot/vmlinuz-2.6.21-1.3228.fc7 ro root=LABEL=/ rhgb
> quiet
>         initrd /boot/initrd-2.6.21-1.3228.fc7.img
> when booted does support cpu scaling and dose shut off when I do a  shut
> down.
> Any explanations of this difference? Please don't laugh since I have
> been telling people how to get their machines to shut off and I have
> been  hosted on my own petard.
> By the way what is the significance of the extra lines in the grub
> clause for the xen kernel?

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