Re: [Xen-users] Memory allocation

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> Upgraded my xen box to a gb of ram and had a bit of trouble expanding
> usage with baloon and maxmem.  I figure I'm just being blond so I cut
> straight to teh chase and tweek the memory settings in the configuration
> files for each vm.

It should work...  But you have to have set the max memory you might balloon 
to (I think the parameter is mem=) on the domain's kernel command line.  If 
you don't do that, Linux will make its memory map to small and it won't be 
able to grow beyond its initial allocation.

> everything goes fine except for the last domU.  can't allocate memory is
> the error reported.  I check my math and I'm 5mb under my physical
> memory. I go through a couple of small reductions of memory usage to no
> avail.  after a bigger decrease on the last domU memory allocation, all
> domU's run.
>
> 1) how can one determine how much memory is really available for domU's?

xm info tells you how much is *really* free in the machine

> 2) how much memory is really used by a domU?

Basically what its allocation is + a few (smallish) book-keeping structures in 
dom0 and Xen.

Xen itself can take up to about 40MB (won't be quite that large on your 
machine).

> 3) in the furture, could memory be allocated as a percentage of total
> memory?

That's a simple patch, so it's quite doable.

Do you fancy starting a wishlist section on the wiki?  Or filing a "wishlist" 
item in the bugzilla if such a thing exists (not sure it does at the moment).

Cheers,
mark

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