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xen-ia64-devel
Re: [Xen-ia64-devel] How many memory can assign to xen0?
On Fri, 2006-04-21 at 13:34 +0200, Tristan Gingold wrote:
> Le Vendredi 21 Avril 2006 13:15, You, Yongkang a écrit :
> > Hi all,
> >
> > I found Xen booting would hang, if I assign a little large memory (>1900M)
> > to Xen0. The hang happened just after printing "load initrd..."
> >
> > Firstly I try it in a 2G physical memory box. The results:
> > dom0_mem=1000M booting ok
> > =1024M booting ok
> > =1800M booting ok (xm info show there are 66M free memory left)
> > =1900M booting hang
> > =2000M __booting hang__
> > =2048M __booting hang__
> Seems correct.
> Xen needs at least 64MB (Xenheap) plus about 1 MB for the code.
> Also a few MB are lost due to WB attributes, PAL, SAL and EFI use.
I've seen similar issues on zx1 systems. Except zx1 only has ~1GB of
contiguous memory in the low address range, so the limit is 880MB.
> (XEN) alloc_dom0: starting (initializing 2048 MB...)
> (XEN) alloc_dom0: can't allocate contiguous memory size=2147483648
>
> I suppose this issue may be fixed with VP.
Yes and no. With p2m/vp, if I specify a larger dom0_mem= size, the
allocation shifts to a range >4GB if it cannot be completely satisfied
in low memory. Without some low memory dom0 fails to allocate a range
for the swiotlb and dies. At some point we need to make the dom0 MDT
creation code smarter to be able to handle more elaborate scenarios.
Currently it wants to provide dom0 all it's memory in a single MDT
entry. Thanks,
Alex
--
Alex Williamson HP Linux & Open Source Lab
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