WARNING - OLD ARCHIVES

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/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] Linux mainstream balloon driver fails to grow memory= ->

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Subject: Re: [Xen-devel] Linux mainstream balloon driver fails to grow memory= -> maxmem=
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Mon, 23 Aug 2010 17:50:49 -0700
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Daniel Kiper <dkiper@xxxxxxxxxxxx>, Vasiliy G Tolstov <v.tolstov@xxxxxxxxx>
Delivery-date: Mon, 23 Aug 2010 17:51:19 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <a8aa7cb8-1f20-44ec-a6d5-72e991b0bb6f@default>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <a8aa7cb8-1f20-44ec-a6d5-72e991b0bb6f@default>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.7) Gecko/20100720 Fedora/3.1.1-1.fc13 Lightning/1.0b2pre Thunderbird/3.1.1
 On 08/23/2010 04:49 PM, Dan Magenheimer wrote:
> Hi Jeremy --
>
> Vasiliy discovered (and I confirmed) that the mainstream
> Linux balloon driver won't balloon above the initial
> memory with which the Linux guest was launched.  E.g.
> a 2.6.34 guest launched with these in vm.cfg:
>
> memory=1024
> maxmem=1536
>
> displays properly in xentop, but changing target_kb
> in /sys/devices/system/xen_memory/xen_memory0
> doesn't "take" for any value greater than 1024*1024.
>
> We tested with 2.6.34 but it even fails in RHEL6 Beta2.
>
> Is this a known problem/bug (or maybe a feature)?

Known bug.  There's no machinery in there to allocate enough struct
pages for maxmem, only for "memory".

The immediately workaround is to start the domain with fully populated
"memory" and then have it balloon out the unwanted stuff asap, but it
does mean you need to have enough memory to start with.

There's a couple of experiments floating around in the tree to try to
honour maxmem, but they're somewhat rotted.  Its probably worth trying
to resurrect them though.

And of course there's Daniel's work which is a more flexible
andcomprehensive approach, but it does rely on hotplug memory (which has
its own overheads).

    J

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel