Re: [Xen-devel] Re: XenParavirtOps wiki page updates

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Ferenc Wagner wrote:
> Thanks for collecting this very useful bunch of information!
> Here is what I still miss:
>
>  * Features in 2.6.26:
>      Balloon (contraction only)
>
>    It isn't clear whether this contraction is reversible or not.
>   
It is, but only up to the original size.

>  * If the domain crashes very early, before any output appears on the
>    console, then booting with: should provide some useful information.
>
>    Booting with what?
>   
earlyprintk=xen

>  * How to achieve time sync between the dom0 and the domUs?  Lots of
>    people seem to have problem with domU clock drift, me included.
>    Ntp doesn't work in domU, and apparently no clocksource guarantees
>    such synchronization.
>   
Why doesn't ntp work?  As far as I know it should.

The 2.6.18-xen kernels have a mechanism to try and sync the domains to 
the hypervisor's time, but it doesn't fit well into the current kernel's 
timekeeping.  I think either ntp or a lightweight daemon should be able 
to do this from usermode.  (I was thinking of adding some /sys files to 
publish the hypervisor's current time, which a daemon could use to warp 
the domain's time to match.)
>  * I couldn't find it documented anywhere that SysRq is available via
>    Ctrl+O on the domU and more importantly on the dom0 serial console.
>
>  * The idle count doubling I still experience happens with pvops
>    guests only (http://lkml.org/lkml/2008/9/18/276).
>   
That is pretty strange.

> Otherwise, Debian's pvops guest kernel works very good for me, already
> in production.
>   
Good to hear.  32 or 64 bit?

   J

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