Re: [Xen-users] PVH for debian guest

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Sun, Jan 17, 2016 at 4:40 PM, ÃliÃs TamÃs <et@xxxxxxx> wrote:
> Hi.
>
> I wouldlike to receive the list's opinion about XEN PVH mode for LINUX
> guests. The dom0 is a linux (running dom0pvh) and the guests are also
> linux machines.
>
> Up to these days I had the opnion that there is nothing that can be
> faster then PV, But on the net I found somany articles and benchmarks,
> but none of them says anything about PVH-based linux guest.
>
>
> Some time ago on this list I read, that someone has tried it and
> suprisingly he got better results with hw assisted virtualized system
> calls, then the native PV ones. Could someone enlighten me?
>
> Is it worth setting the
> "pvh=1" parameter for linux guests? (I tried, practically this is the
> only change I need to make to utilize this new mode). So it seems to be
> an easy win. But is it a win for linux guests? Sould oi stay with PV or
> go to PVH?

You should also be aware that PVH is still marked "experimental", and
is actually going through an architectural overhaul at the moment.
Until it's marked as "supported":
1. PVH may not be stable or have optimal performance
2. It may break and / or require a kernel upgrade when you do a Xen upgrade.

Regarding #1, YMMV.  I haven't seen any numbers on the existing PVH
system in a while because of the architectural overhaul (which makes
all such measurements obsolete).

 -George

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