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


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

To: Xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] memory=x & maxmem=y
From: Paul Archer <tigger@xxxxxx>
Date: Sat, 19 May 2007 23:34:38 -0500 (CDT)
Delivery-date: Mon, 21 May 2007 10:17:15 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
List-help: <mailto:xen-users-request@lists.xensource.com?subject=help>
List-id: Xen user discussion <xen-users.lists.xensource.com>
List-post: <mailto:xen-users@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
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.

According to Jayson Vantuyl in a discussion on this list a few days ago:
"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."

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?

Paul Archer

"I'll say this about Linux: it's the first time I've seen Unix on the right platform."--Steve Ballmer, president of Microsoft
(NB: Microsoft used to own SCO, which did, and still does,
produce a Unix for the Intel platform.)

Xen-users mailing list

<Prev in Thread] Current Thread [Next in Thread>