RE: [Xen-ia64-devel] Xen is now runnnig at Bull

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

Actually, it is conceivable that a single processor
machine would want to support more than 64 VMs so
it is very likely that a 48 processor machine would.
The limit of 64 is on the number of domains that
might be active, not necessarily simultaneously active.

I don't think rid virtualization helps here as there
are only 2**24 rids available and every domain will
use as many as it is given.  And there's no way to garbage
collect rids from a domain. So -- I think -- the only ways
to support more than 64 domains are:
1) Give each domain fewer than 2**18 rids, or
2) Flush the TLB whenever "necessary" when switching domains

The frequency of "necessary" could be reduced by using
a processor affinity hierarchy of some kind.  I suppose
this is a form of rid virtualization, but is more like
an extension (e.g. like PAE).

Dan


> -----Original Message-----
> From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf 
> Of Dong, Eddie
> Sent: Thursday, September 08, 2005 4:01 AM
> To: Tristan Gingold; xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-ia64-devel] Xen is now runnnig at Bull
> 
> Tristan Gingold wrote:
> > Le Jeudi 08 Septembre 2005 04:59, Dong, Eddie a écrit :
> >> Tristan:
> >>> Since Bull sells big SMP/NUMA machine (32 procs), we are 
> interested
> >>> in the SMP developement.  I will start to work on SMP soon.
> >> 
> >> So how many VMs are u preparing to support?
> > Good question.
> > The machine has 12 montecito.  This means 48 LP.
> > So, we should be able to support at least 48 UP VMs :-)
> > 
> > Tristan.
> If you want to support more than 63VMs, you need rid 
> virtualization that is previously discussed. But current it 
> is still OK as you needs 48 VMs :-)
> Eddie
> 
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