Re: [Engine-devel] [vdsm] reserve virtio-balloon device created by libvirt

On Sun, Apr 29, 2012 at 07:24:52AM -0400, Andrew Cathrow wrote: > > > ----- Original Message ----- >> From: "Dan Kenigsberg"<danken(a)redhat.com> >> To: "Gal Hammer"<ghammer(a)redhat.com> >> Cc: vdsm-devel(a)lists.fedorahosted.org >> Sent: Sunday, April 29, 2012 7:19:10 AM >> Subject: Re: [vdsm] reserve virtio-balloon device created by libvirt >> >> On Mon, Apr 23, 2012 at 04:00:55PM +0300, Gal Hammer wrote: >>> On 23/04/2012 12:26, Mark Wu wrote: >>>> Hi guys, >>>> >>>> I saw that an option to create balloon device was added by Gal in >>>> http://gerrit.ovirt.org/1573 >>>> I have a question about it. Why don we preserve the old default >>>> behaviour? I know it's not supported by ovirt-engine now, but I >>>> can't >>>> figure out what will break if it's not disabled explicitly. So do >>>> you >>>> think we can just make use of the balloon device added by libvirt? >>> >>> We didn't change the old behavior. >>> >>> Libvirt creates by default a memory-balloon device, so vdsm >>> defaults >>> was to disable it by adding a "none"-type device. This was done >>> because vdsm didn't include an option to add such device. >>> >>> My patch added an option to create a memory-balloon through vdsm. >>> If >>> the user didn't request to add the device, the behavior is same as >>> before, disabling the memory-balloon. >> >> I feel that it would be best not to flip Vdsm's default at the >> moment, >> even though it is the opposite of libvirt's. I would consider to flip >> them only after your (Mark's) patches are in, tested, and proven >> worthwhile for the common case. >> >> Currently, without any management for the balloon, reserving a guest >> PCI >> device was deemed wasteful. > > On the other side of the fence > - We know that we do need to do ballooning > - In the (next?) release we'll end up adding this support > - There's no harm (see next point) in adding the device now in fact it saves a config change on upgrade. Well, there is a surprise factor, for someone running a guest generated in a previous version. Suddenly, after Vdsm upgrade, it would see an additional device. At the least, I would like Vdsm to have a configurable option to keep the old behavior.

> - While it takes up a PCI slot it's going to be very, very rare deployments that will ever see the limit, libvirt/virtmanager/virt-install has done this forever without seeing push back. _______________________________________________ vdsm-devel mailing list vdsm-devel(a)lists.fedorahosted.org https://fedorahosted.org/mailman/listinfo/vdsm-devel