[Users] ovirt 3.3.1 all VMs boot on the same host?

[Gilad Chaplik]

----- Original Message -----
> From: "Gilad Chaplik" <gchaplik at redhat.com>
> To: "Gianluca Cecchi" <gianluca.cecchi at gmail.com>
> Cc: "users" <users at ovirt.org>
> Sent: Tuesday, November 26, 2013 9:48:37 AM
> Subject: Re: [Users] ovirt 3.3.1 all VMs boot on the same host?
> 
> ----- Original Message -----
> > From: "Gianluca Cecchi" <gianluca.cecchi at gmail.com>
> > To: "Doron Fediuck" <dfediuck at redhat.com>
> > Cc: "users" <users at ovirt.org>, "Gilad Chaplik" <gchaplik at redhat.com>
> > Sent: Tuesday, November 26, 2013 12:32:13 AM
> > Subject: Re: [Users] ovirt 3.3.1 all VMs boot on the same host?
> > 
> > On Mon, Nov 25, 2013 at 4:50 PM, Doron Fediuck wrote:
> > 
> > >
> > > Hi Gianluca,
> > > KSM comes with qemu-kvm, so no point of looking for it as an rpm:
> > > # rpm -ql qemu-kvm | grep ksm
> > > /etc/ksmtuned.conf
> > > /etc/rc.d/init.d/ksm
> > > /etc/rc.d/init.d/ksmtuned
> > > /etc/sysconfig/ksm
> > > /usr/sbin/ksmtuned
> > >
> > > As for the actual issue, which cluster policy are you using now?
> > > See the attached to illustrate what I'm referring to.
> > 
> > Are you talking about RHEL 6.x?
> > Because on my Fedora 19 hosts (despite their names containing f18...)
> > I see this:
> > 
> > [root at f18ovn03 ~]# ls -l /etc/sysconfig/ksm
> > ls: cannot access /etc/sysconfig/ksm: No such file or directory
> > 
> > [root at f18ovn03 ~]# rpm -ql qemu-kvm
> > (contains no files)
> > 
> > [root at f18ovn03 ~]# yumdownloader ksm
> > 
> > [root at f18ovn03 ~]# rpm -qpl ksm-1.4.2-13.fc19.x86_64.rpm
> > /etc/ksmtuned.conf
> > /etc/sysconfig/ksm
> > /lib/systemd/ksmctl
> > /lib/systemd/system/ksm.service
> > /lib/systemd/system/ksmtuned.service
> > /usr/sbin/ksmtuned
> > 
> > [root at f18ovn03 ~]# rpm -qpi ksm-1.4.2-13.fc19.x86_64.rpm
> > Name        : ksm
> > Epoch       : 2
> > Version     : 1.4.2
> > Release     : 13.fc19
> > Architecture: x86_64
> > Install Date: (not installed)
> > Group       : Development/Tools
> > Size        : 12035
> > License     : GPLv2+ and LGPLv2+ and BSD
> > Signature   : RSA/SHA256, Wed 06 Nov 2013 08:02:15 PM CET, Key ID
> > 07477e65fb4b18e6
> > Source RPM  : qemu-1.4.2-13.fc19.src.rpm
> > Build Date  : Wed 06 Nov 2013 02:11:41 AM CET
> > Build Host  : buildvm-07.phx2.fedoraproject.org
> > Relocations : (not relocatable)
> > Packager    : Fedora Project
> > Vendor      : Fedora Project
> > URL         : http://www.qemu.org/
> > Summary     : Kernel Samepage Merging services
> > Description :
> > Kernel Samepage Merging (KSM) is a memory-saving de-duplication feature,
> > that merges anonymous (private) pages (not pagecache ones).
> > 
> > This package provides service files for disabling and tuning KSM.
> > 
> > As for the current cluster config:
> > - optimization : none (disable memory page sharing)
> > memory balloon optimization is not checked
> > 
> > - resilience policy : migrate virtual machines
> > 
> > - cluster policy : none
> 
> Hi Gianluca,
> 
> When there is no policy selected, we try to sort the VMs according to host
> CPU load.
> Probably the host data (CPU load) wasn't fetched, and then it selects the
> non-spm host (because both of them had zero cpu load).
> 
> I we do some testing and get back to you.
> 
> Thanks, Gilad.

Hi Gianluca,

In oVirt 3.3, the scheduler had some transformation of how we compare hosts for VM scheduling.
In previous versions the comparisons used to be on real numbers and now we use weight functions that generates
integers, so somewhere in the rounding up of that numbers, we miss some crucial fractions that used to compare the hosts better.

opened a bug for it:
https://bugzilla.redhat.com/1040460

Thanks for your feedback!

> > 
> > It seems to me that when I was in 3.2 there was some sort of load
> > balancing in the sense that if I powered on in sequence 3 VM they
> > started one on a host and one on the other.
> > So that now I noticed sort of difference.
> > I didn't change anything in cluster policy after upgrade to 3.3.1
> > 
> > Gianluca
> > 
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