[CentOS-virt] Xen Balloon Driver on PVHVM CentOS6

Tue Jul 16 13:18:26 UTC 2013
Rushikesh Jadhav <2rushikeshj at gmail.com>

On Tue, Jul 16, 2013 at 3:26 PM, David Vrabel <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 repo
> > needs to support as both Guest and Host (Dom0).
>
> The kernel is only intended for use as a dom0 kernel.  We recommend the
> use of the existing 2.6.32 kernel for guests.
>
>
Any idea for not using 3.4.50 as guest kernel ?
2.6.32 is giving lot of trouble in ballooning, I have filed below bugs for
it.
https://bugzilla.redhat.com/show_bug.cgi?id=969601
http://bugs.centos.org/view.php?id=6484

Please have a look at comment
https://bugzilla.redhat.com/show_bug.cgi?id=969601#c2



> > The kernel had to be recompiled with CONFIG_XEN_SELFBALLOONING.
> > How can I request to make it default enable in centos repo ? or is there
> > any reason to not have it default ?
>
> We do not want self-ballooning enabled in the dom0 kernel.  This option
> is also not required for toolstack-directed ballooning.
>

I'm currently using only xl toolstack and not using XAPI/Xenserver
toolstack, I have both environments and intent to fix in both.
Since 2.6.32 is not ballooning, I had to find another kernel which supports
this. 3.4.50 seems to be working in Xenserver but does not work on native
Xen,

I'm using centos-release-xen repo to setup host ( dom0 CentOS6 + 3.4.50 )
 & guest ( domU CentOS6 + 3.4.50 ).
In my testing it was observed that if CONFIG_XEN_SELFBALLOONING is not set
then the guest does not balloon. ( Verified by xl mem-set )

Problem may be with CONFIG_XEN_BALLOON_MEMORY_HOTPLUG=y as well. What do
you think ?
I'll try to disable selfballooning and test with
only CONFIG_XEN_BALLOON_MEMORY_HOTPLUG.

Thanks.



>
> > On Fri, Jul 12, 2013 at 7:42 PM, Rushikesh Jadhav <2rushikeshj at gmail.com
> > <mailto:2rushikeshj at gmail.com>> wrote:
> >
> >     Hi List,
> >
> >     I'm trying to work out the balloon driver on CentOS6 HVM but it
> >     seems to be not working with default 2.6.32 or newer 3.4 kernel.
> >
> >     Does balloon driver work on HVM linux guests with Linux Kernel 3.4
> >     from centos repo ?
> >
> >     PV is fine and is able to balloon.
> >
> >     My host is Xen 4.1.2 with dom0 as 3.4.46-8.el6.centos.alt.x86_64
> >     My guest is CentOS6.4 with kernel 3.4.46-8.el6.centos.alt.x86_64
> >
> >     Please have a look at below guest logs,
> >     [root at hvmc6 ~]# uname -a Linux hvmc6 3.4.50-8.el6.centos.alt.x86_64
> >     #1 SMP Fri Jun 21 03:14:22 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
> >     [root at hvmc6 ~]# xenstore-ls memory initial-reservation = "1193984"
> >     initial-target = "1048576" static-max = "16777216" target =
> >     "1048576" dynamic-min = "1048576" dynamic-max = "1048576"
> >     memory-offset = "-258100"
> >     [root at hvmc6 ~]# dmesg | grep -i balloon xen/balloon: Initialising
> >     balloon driver. xen-balloon: Initialising balloon driver.
> >     [root at hvmc6 ~]# free -m total used free shared buffers cached Mem:
> >     463 221 241 0 24 13 -/+ buffers/cache: 184 278 Swap: 9987 7 9980
>
> It's not clear what sequence of toolstack operations you've done prior
> to the above commands.  Are you trying to increase or decrease the
> amount of memory in the guest, what were the toolstack commands you used
> and what is the initial guest configuration.
>
> >     When I try to set it manually from host, I get
> >     # xl mem-set 229 2049 xc: error: do_memory_op: WARNING: op=16 not
> >     converted to safe ioctls: Internal error
>
> This (harmless) warning only occurs on XenServer hosts.  What host are
> you actually running?
>
> David
>
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