Re: [Xen-users] allocating memory to dom0

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> Hey chaps, having a minor dispute with a friend. According the README
> in the Xen sources....

I'm getting an amusing mental image of people all over the world, in the pub, 
ignoring the football scores and arguing about Xen with their mates :-)

> "
>    The Xen command line takes a number of optional arguments described
>    in the manual. The most common is 'dom0_mem=xxxM' which sets the
>    amount of memory to allocate for use by your initial virtual
>    machine (known as domain 0). Note that Xen itself reserves about
>    32MB memory for internal use, which is not available for allocation
>    to virtual machines.
> .."
>
> I've taken this to mean that one allocates say, half of one's RAM to
> dom0 with the command `dom0_mem=xxxM`. The domUs will then use up to
> the other half of the box's RAM. Is this correct?
>
> My buddy says that this is unnecessary as the dom0 only needs 32M of
> ram. It will give the RAM away to the domU chaps until it has no more
> RAM to spare.

Both correct.

You can either set the dom0 memory on the commandline leaving the rest 
available to domUs (this was the standard mode of operation for a long time), 
or you can have dom0 take all the memory, then balloon itself down to make 
room for other guests.  The auto-ballooning code also allows you to specify a 
minimum size dom0 will balloon down to (auto-ballooning might be default on 
now, I think, but you don't have to use it).

HTH,
Mark

-- 
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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