Re: [Xen-API] Plans for 64 bit dom0

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Wed, May 29, 2013 at 09:11:38AM +0000, James Bulpin wrote:
> On Tue, May 28, 2013 at 21:28, Pasi wrote:
> > On Tue, May 28, 2013 at 01:22:04PM -0500, Phil Ritter wrote:
> > >    Are there any plans to deliver a packaged version of XCP (the ISO
> > version)
> > >    with dom0 built on a 64 bit kernel?
> > >    64-bit is becoming more and more important for supporting some new
> > device
> > >    drivers and storage technology.  Also existing 32 bit dom0 is showing
> > its
> > >    weakness under heavy I/O workloads.
> > >    Debian xcp-xapi is not a good option yet as there are just enough
> > >    differences to make it hard to manage.
> > >    Perhaps hope for 64-bit in 1.7 release?
> > >
> > 
> > I'm guessing 64bit dom0 will be used in XCP after Xen PVH (hybrid) support
> > is merged to
> > upstream Xen and upstream Linux kernel, so most probably around Xen 4.4
> > timeframe.
> > 
> > Xen PVH support allows running dom0 in an HVM container.
> 
> I suspect it'll take a while for that to stabilise enough for an 
> enterprise-class virtualization platform to use it so I wouldn't expect XCP 
> to use PVH dom0 for a while after its initial release.
> 

That's true.

> However moving to a 64 bit PV dom0 is a realistic possibility - Citrix 
> performance testing has shown that the known 64 bit micro-level slowdown 
> (syscalls) doesn't have an appreciable effect on the system-level performance 
> for most metrics. There were some notable slowdowns but generally on 
> relatively uncommon operations like writing to syslog. The conclusion from 
> the study was that moving to a 64 bit PV dom0 would be OK from a performance 
> perspective.
> 
> Therefore the current intention is to move XCP to 64 bit PV dom0 later this 
> year, at the same time we move to a 3.x kernel. 
> I'm hoping that trunk builds (pre-stabilisation) will be available well ahead 
> of full release to give people a chance to try them out.
> 

Great!

-- Pasi


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