* Xen max supported memory per guest VM?
@ 2010-08-14 18:42 Pasi Kärkkäinen
2010-08-14 21:18 ` Keir Fraser
0 siblings, 1 reply; 7+ messages in thread
From: Pasi Kärkkäinen @ 2010-08-14 18:42 UTC (permalink / raw)
To: xen-devel
Hello,
In http://wiki.xensource.com/xenwiki/Xen4.0 we mention the following:
"Better performance and scalability: 128 vcpus per guest, 1 TB of RAM per host, 128 physical CPUs per host (as a default, can be compile-time increased to lots more)."
But what's the max supported amount of memory for a (64bit) guest?
-- Pasi
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: Xen max supported memory per guest VM?
2010-08-14 18:42 Xen max supported memory per guest VM? Pasi Kärkkäinen
@ 2010-08-14 21:18 ` Keir Fraser
2010-08-14 21:30 ` Pasi Kärkkäinen
2010-08-16 9:04 ` Jan Beulich
0 siblings, 2 replies; 7+ messages in thread
From: Keir Fraser @ 2010-08-14 21:18 UTC (permalink / raw)
To: Pasi Kärkkäinen, xen-devel
On 14/08/2010 19:42, "Pasi Kärkkäinen" <pasik@iki.fi> wrote:
> Hello,
>
> In http://wiki.xensource.com/xenwiki/Xen4.0 we mention the following:
> "Better performance and scalability: 128 vcpus per guest, 1 TB of RAM per
> host, 128 physical CPUs per host (as a default, can be compile-time increased
> to lots more)."
>
> But what's the max supported amount of memory for a (64bit) guest?
Allocating the whole 1TB should work. It's unlikely to have been tested
though.
-- Keir
> -- Pasi
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: Xen max supported memory per guest VM?
2010-08-14 21:18 ` Keir Fraser
@ 2010-08-14 21:30 ` Pasi Kärkkäinen
2010-08-14 21:46 ` Keir Fraser
2010-08-16 9:04 ` Jan Beulich
1 sibling, 1 reply; 7+ messages in thread
From: Pasi Kärkkäinen @ 2010-08-14 21:30 UTC (permalink / raw)
To: Keir Fraser; +Cc: xen-devel
On Sat, Aug 14, 2010 at 10:18:11PM +0100, Keir Fraser wrote:
> On 14/08/2010 19:42, "Pasi Kärkkäinen" <pasik@iki.fi> wrote:
>
> > Hello,
> >
> > In http://wiki.xensource.com/xenwiki/Xen4.0 we mention the following:
> > "Better performance and scalability: 128 vcpus per guest, 1 TB of RAM per
> > host, 128 physical CPUs per host (as a default, can be compile-time increased
> > to lots more)."
> >
> > But what's the max supported amount of memory for a (64bit) guest?
>
> Allocating the whole 1TB should work. It's unlikely to have been tested
> though.
>
Ok. I guess it might also have a difference if it's a PV or HVM guest..
-- Pasi
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: Xen max supported memory per guest VM?
2010-08-14 21:30 ` Pasi Kärkkäinen
@ 2010-08-14 21:46 ` Keir Fraser
0 siblings, 0 replies; 7+ messages in thread
From: Keir Fraser @ 2010-08-14 21:46 UTC (permalink / raw)
To: Pasi Kärkkäinen; +Cc: xen-devel
On 14/08/2010 22:30, "Pasi Kärkkäinen" <pasik@iki.fi> wrote:
>>> In http://wiki.xensource.com/xenwiki/Xen4.0 we mention the following:
>>> "Better performance and scalability: 128 vcpus per guest, 1 TB of RAM per
>>> host, 128 physical CPUs per host (as a default, can be compile-time
>>> increased
>>> to lots more)."
>>>
>>> But what's the max supported amount of memory for a (64bit) guest?
>>
>> Allocating the whole 1TB should work. It's unlikely to have been tested
>> though.
>>
>
> Ok. I guess it might also have a difference if it's a PV or HVM guest..
I can't think of a reason we'd be limited to less for HVM or PV.
-- Keir
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: Xen max supported memory per guest VM?
2010-08-14 21:18 ` Keir Fraser
2010-08-14 21:30 ` Pasi Kärkkäinen
@ 2010-08-16 9:04 ` Jan Beulich
2010-08-16 9:18 ` Keir Fraser
1 sibling, 1 reply; 7+ messages in thread
From: Jan Beulich @ 2010-08-16 9:04 UTC (permalink / raw)
To: Keir Fraser, pasik; +Cc: xen-devel
>>> On 14.08.10 at 23:18, Keir Fraser <keir.fraser@eu.citrix.com> wrote:
> On 14/08/2010 19:42, "Pasi Kärkkäinen" <pasik@iki.fi> wrote:
>
>> Hello,
>>
>> In http://wiki.xensource.com/xenwiki/Xen4.0 we mention the following:
>> "Better performance and scalability: 128 vcpus per guest, 1 TB of RAM per
>> host, 128 physical CPUs per host (as a default, can be compile-time increased
>> to lots more)."
>>
>> But what's the max supported amount of memory for a (64bit) guest?
>
> Allocating the whole 1TB should work. It's unlikely to have been tested
> though.
Not everything will work with more than 512G: Anything that wants
to access the guest's pfn_to_mfn_frame_list_list won't work, as
there's no specification of how more than a page worth of these top
level pointers should be expressed. Affected would be (afaict) save/
restore/migrate, kexec, and dumping of a crashed guest.
Jan
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: Xen max supported memory per guest VM?
2010-08-16 9:04 ` Jan Beulich
@ 2010-08-16 9:18 ` Keir Fraser
2010-08-16 9:34 ` Pasi Kärkkäinen
0 siblings, 1 reply; 7+ messages in thread
From: Keir Fraser @ 2010-08-16 9:18 UTC (permalink / raw)
To: Jan Beulich, pasik; +Cc: xen-devel
On 16/08/2010 10:04, "Jan Beulich" <JBeulich@novell.com> wrote:
>>> But what's the max supported amount of memory for a (64bit) guest?
>>
>> Allocating the whole 1TB should work. It's unlikely to have been tested
>> though.
>
> Not everything will work with more than 512G: Anything that wants
> to access the guest's pfn_to_mfn_frame_list_list won't work, as
> there's no specification of how more than a page worth of these top
> level pointers should be expressed. Affected would be (afaict) save/
> restore/migrate, kexec, and dumping of a crashed guest.
Okay, so that's a further restriction on PV guests. HVM guests should
theoretically still be good up to 1TB.
-- Keir
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: Xen max supported memory per guest VM?
2010-08-16 9:18 ` Keir Fraser
@ 2010-08-16 9:34 ` Pasi Kärkkäinen
0 siblings, 0 replies; 7+ messages in thread
From: Pasi Kärkkäinen @ 2010-08-16 9:34 UTC (permalink / raw)
To: Keir Fraser; +Cc: xen-devel, Jan Beulich
On Mon, Aug 16, 2010 at 10:18:53AM +0100, Keir Fraser wrote:
> On 16/08/2010 10:04, "Jan Beulich" <JBeulich@novell.com> wrote:
>
> >>> But what's the max supported amount of memory for a (64bit) guest?
> >>
> >> Allocating the whole 1TB should work. It's unlikely to have been tested
> >> though.
> >
> > Not everything will work with more than 512G: Anything that wants
> > to access the guest's pfn_to_mfn_frame_list_list won't work, as
> > there's no specification of how more than a page worth of these top
> > level pointers should be expressed. Affected would be (afaict) save/
> > restore/migrate, kexec, and dumping of a crashed guest.
>
> Okay, so that's a further restriction on PV guests. HVM guests should
> theoretically still be good up to 1TB.
>
Ok, I updated this info to:
http://wiki.xensource.com/xenwiki/Xen4.0
-- Pasi
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2010-08-16 9:34 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2010-08-14 18:42 Xen max supported memory per guest VM? Pasi Kärkkäinen
2010-08-14 21:18 ` Keir Fraser
2010-08-14 21:30 ` Pasi Kärkkäinen
2010-08-14 21:46 ` Keir Fraser
2010-08-16 9:04 ` Jan Beulich
2010-08-16 9:18 ` Keir Fraser
2010-08-16 9:34 ` Pasi Kärkkäinen
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