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Re: [Xen-users] Memory Ballooning / Overcommitting

To: xen-users <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Memory Ballooning / Overcommitting
From: Chris Hane <chrishane@xxxxxxxxx>
Date: Tue, 22 Jul 2008 14:34:45 -0400
Cc: Matt Ayres <matta@xxxxxxxxxxxx>
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Matt Ayres wrote:
Robert Read wrote:

On Jul 17, 2008, at 16:35 , Chris Hane wrote:

I have a xen server setup that I want to install a lot of vms on if possible. The vms will have no utilization for the most part; and brief utilization when active. The server has 2GB of RAM.

We were running into a problem were the dom0 would not let us add anymore vms because we were out of physical memory.

I have started to read about memory ballooning and hoping someone could point me in the right direction. If my understanding is correct, ballooning will increase the vm memory if needed up to a maxmem setting. And can decrease memory if requested by the dom0.

Is this an automatic process, or do I have to manually issue a command to increase/decrease the domU memory? The command I know about is:
> xm mem-set <Domain> <Mem>

There is no automatic process for increasing guest memory, yet. As Mark mentioned yesterday there are some patches floating around to do this if someone wants to try it out.
xenballoond was committed to xen-unstable for the next release. It was designed for pretty much this exact reason.

Details: http://wiki.xensource.com/xenwiki/Open_Topics_For_Discussion?action=AttachFile&do=get&target=Memory+Overcommit.pdf


I have read the pdf you linked to and am excited to try out the scripts. One question, do you know if the scripts rely on functionality/interfaces in xen-unstable or could the potentially work on xen 3.x (I am running 3.1.4)?

Thanks for pointing me to this.


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