[CentOS-virt] Xen Balloon Driver on PVHVM CentOS6
2rushikeshj at gmail.com
Thu Jul 18 14:12:47 UTC 2013
On Wed, Jul 17, 2013 at 5:42 PM, David Vrabel <david.vrabel at citrix.com>wrote:
> On 16/07/13 14:18, Rushikesh Jadhav wrote:
> > On Tue, Jul 16, 2013 at 3:26 PM, David Vrabel <david.vrabel at citrix.com
> > <mailto:david.vrabel at citrix.com>> wrote:
> > On 15/07/13 20:44, Rushikesh Jadhav wrote:
> > > Hi List,
> > >
> > > It seems that the xen balloon functionality for guest is not
> > enabled in
> > > CentOS 3.4.50-8.el6 xen kernel by default via
> > centos-release-xen.x86_64
> > > repo. I think this should have been present since this extra Xen
> > > needs to support as both Guest and Host (Dom0).
> > The kernel is only intended for use as a dom0 kernel. We recommend
> > use of the existing 2.6.32 kernel for guests.
> > Any idea for not using 3.4.50 as guest kernel ?
> The specific 3.4 kernel provided as part of the Xen4CentOS project as a
> configuration selected for use as a dom0 kernel and thus it may not have
> guest-centric options (like ballooning) correctly configured.
> > Problem may be with CONFIG_XEN_BALLOON_MEMORY_HOTPLUG=y as well. What do
> > you think ?
> CONFIG_XEN_BALLOON_MEMORY_HOTPLUG=y is required to allow most Linux PV
> guests to balloon above their initial allocation. However, it is broken
> in some cases when enabled in a dom0 kernel and has been disabled.
Can we enable it with a code check for xen_initial_domain() ?
We really need an authenticated guest Centos kernel which has bug free
ballooning as Xen guest.
KVM or HVM Xen is fine but PV will always suffer till CentOS/RHEL switches
I don't have any news on CentOS7 or RHEL7.
> As a workaround I would suggest starting all guests with an initial
> allocation that corresponds to the maximum they may ever use. You can
> then immediately balloon them down.
This workaround works good only while first boot. If the guest gets
rebooted after balloon down then the base memory is changed to last known
allocated memory. After reboot the guest wont be able to balloon up.
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