Re: [Xen-users] Xen 3.0.0 32bit-pae (testing changeset 8270) crashes(pgtable.c:284, kernel bug?)

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> Is it possible to have > 3.5G available to DomU-s with xen 2? I`ve recently
> upgraded a server from 2 to 4 GB RAM and xen only sees 3455MB?

Nope, Xen 2 doesn't do PAE or 64-bit.  If you can only see 3.5 Gig that's 
because your firmware has allocated a half gig memory hole for IO regions 
etc.  Unfortunately you'll need the ability to address >4Gig physically in 
order to get to all your RAM, either PAE or 64-bit would be fine.

Bottom line: you'd need Xen 3 to be able to access all your memory.

Cheers,
Mark

> On Thursday 02 February 2006 17:50, Matt Ayres wrote:
> > Ian Pratt wrote:
> > >> 3.0.1 seems to fix the bug I saw on my two machines, but now
> > >> there is another
> > >> (but somehow related) problem for me in 3.0.1-pae. I don't
> > >> know if it's still
> > >> related to the 3ware controller, but at least it only appears
> > >> for domains
> > >> that have memory above the 32bit adress-space again, so the
> > >> first started
> > >> domUs run fine. The big difference is that I don't have any
> > >> complete freezes
> > >> of the xen machine anymore, just domUs are crashing this time.
> > >
> > > Interesting. It looks like xen is running out of memory below 4GB, and
> > > can't service the domain's request for a new L3 PGD, causing the domain
> > > to bug out.
> > >
> > > Are you using dom0_mem= on the xen command line to constrain dom0's
> > > memory usage or are relying on dom0 releasing memory automatically as
> > > you start other domains? If the latter, I expect dom0 is hogging all
> > > the pages below 4GB. [Grrr, PAE is such a crock...]
> > >
> > > Given that your 3ware controller is already putting pressure on the
> > > bottom 4GB you'd be better off setting your initial dom0 memory at boot
> > > time.
> > >
> > > Please let me know how you get on. BTW: can you get a serial line on
> > > the machine? It might be interesting to see some of xen's memory usage
> > > diagnostics.
> >
> > me me me!  Check my thread with Keir on xen-devel regarding this same
> > issue.  I have full console access (with history logged!) and receive
> > this same problem (PAE, 3ware, <4GB range).  I am now running
> > 3.0-testing.
> >
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-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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