Re: [Xen-users] memory question!

[James Bulpin <James.Bulpin@xxxxxxxxxxxx>]

There are two things here:

1 - support for greater than 4GB of physical RAM. This needs PAE support 
which isn't in the Xen 2.0 series. This will be in 3.0 which will be out 
this summer.
2 - missing memory between 3 and 4GB (your scenario has 3GB already 
allocated and you cannot allocate a further 512MB). I ran into this 
myself recently too. I'm told that it is to do with the BIOS remapping 
regions of memory away from areas of address space used by memory-mapped 
devices (this memory would otherwise be unaddressable and wasted). For 
machines with less than 4GB this isn't a problem for Xen because the 
remapping would be to addresses below 4GB. If you have 4GB then it ends 
up being remapped above 4GB. In this case, you need PAE to get to it.
Run 'xm info', you'll probably see about 3300MB total memory available.

James

DMZ LEISHANGTHEM wrote:
> I have a question about memory. I have 8GB of RAM on a
> Dell PE 1850(usb disabled kernel, cos it gets locked
> up on heavy I/O). My domain0 has only 2 gigs of
> memory. I have 2 guest domains 512 each. Now when i
> try to create a 3rd guest domain of 512, xen wont let
> me do it. My confusion is "Is 4G the max amount of
> memory a domain can  get/ or is 4G the max amout of
> cumulative memory all the domains can get(ie. dom0,
> dom1, dom2... etc..combined all together)." 
>
> can i have my domain0 have 4G ram, and at the same
> time domain1 have 4 G of ram?
>
> thanks
> dmz.
>
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