This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-users] extra = "mem=1024" and maxmem

I'm not sure.

I use it on 3.0.4-tip.  I do not know if it works with earlier versions.

On May 15, 2007, at 6:47 PM, tgh wrote:

I am using xen-3.0.3,and I try to set "memory" and "maxmem" following your discussion,but it does work as expected
Does it only work in xen-3.0.4 and later version,or what should I do ?

could you help me
Thanks in advance

Jayson Vantuyl 写道:
There are really three options.

'extra= "mem=1024"' tells the kernel inside of the domain that it only has a 1GB of memory. This is really not the way to do this. Instead use memory=1024.

"maxmem" tells the hypervisor and the kernel inside of the domain how large it could get. This can be adjusted at any time, but Linux domains don't use it after boot time. The advantage of using this option is that the Linux inside of the domain sizes its internal tables so it can grow to that size. This means that you can dynamically change the amount of memory available inside of the domain.

For example, if you have these options for a domain:


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.

Also, you can always size down a domain below its initial RAM usage to free up memory it is not using, which can be handy on busy or complex production servers.

On May 15, 2007, at 4:43 AM, Denny Schierz wrote:


what is the different between the domU config parameter:

extra = "mem=1024"



is maxmem only available on 3.0.4 and later?

cu denny

Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx <mailto:Xen-users@xxxxxxxxxxxxxxxxxxx>

Jayson Vantuyl
Systems Architect
jvantuyl@xxxxxxxxxxxxxx <mailto:jvantuyl@xxxxxxxxxxxxxx>


Xen-users mailing list

Jayson Vantuyl
Systems Architect

Xen-users mailing list