Re: [Xen-users] memory=x & maxmem=y

[Brad Plant <bplant@xxxxxxxxxxxx>]

On Sat, 19 May 2007 23:34:38 -0500 (CDT)
Paul Archer <tigger@xxxxxx> wrote:

> I have been playing with memory= and maxmem=, but I'm not seeing what
> I think I should be seeing, namely that the memory available to a
> domU can be increased on the fly.
> 
> For example, I have:
> memory = 256
> maxmem = 512
> in my config file.
> 
> I can run 'xm mem-set mydomain 128', and the memory in the domU will
> drop to 128. I can run 'xm mem-set mydomain 256' and bring it back up
> to its original memory level. But if I run 'xm mem-set mydomain 512',
> then 'xm list' will see 512M allocated to the domain, but the domain
> will only see 256M. However, if I 'reboot' the domU, when it comes
> back up, it will have 512M of memory.

I'm in the same boat here.

> According to Jayson Vantuyl in a discussion on this list a few days
> ago: "For example, if you have these options for a domain:
> 
> memory=1024
> maxmem=4096
> 
> You will have the kernel boot up with 1GB of memory.  At any point
> you can increase it to, for example, 2 GB with this command:
> 
> xm mem-set <domain> 2048
> 
> The kernel will automagically increase to 2GB of RAM.  This is, as
> you might imagine, extremely cool."
> 
> Is this true? Is it possible to set the initial memory level to be
> something less than maxmem, and have the running (linux) domU see the
> new memory level when it is increased? If so, then is there something
> I'm missing in my setup? A driver in dom0 or domU, perhaps?

I wasn't able to achieve this using xen-3.1. The maximum amount of RAM appears 
to be dictated by the value that the machine is booted with. Has anyone else 
managed to increase the amount of memory allocated to a domU to more than what 
the domU was booted with and have the domU utilise this memory? I.e. show up 
with free -m on the domU?

Cheers,

Brad

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