[one-users] integrating cgroup into OpenNebula-KVM?

[Shi Jin]

Thank you very much Gyula.
I am very interested in learning your solutions. So please post it.

Curious to know, what cgroups subsystems are you using.  I am only
considering cpu. Are you using anything else, like cpuset or memory?

A note on the CPU overcommiting: do you see a problem in overcommitting
single CPU VMs, i.e, multiple small size VMs (vCPU=1) sharing a physical
core? Your note seems to suggest the problem is only with SMP guests.
I think this is a very important feature. And without running multiple VMs
on a single core, I feel there is not much need for cgroups really.  The
current ONE seems good enough if we always set CPU=VCPU in the ONE template.
What I wanted to have is CPU=1 while vCPU=0.5 or even 0.25.

Thanks.
Shi

2010/7/13 Csom Gyula <csom at interface.hu>

> Hi,
> regarding ONE plans I have no clue:) Otherwise in our system (currently
> under development)
> we are using cgroups also (especially we are using it in order to guarantee
> CPU performance
> which is required for vms like web application servers or kinda). We are
> using cgroups in the
> following way:
>
> 1. The vm cpu number is technically bound to VCPU (both at OpenNebula and
> libvirt).
> 2. We are using cpu shares in order to give the proper share.
> 3. We are using the ONE hook system [1] in order to trigger the cgroups
> script.
>
> We are using the following convenctions:
> 4. System share: 90% goes to vms and 10% goes to the system itself.
> 5. We are not overcommiting cpu resources since KVM has problems with such
> environments
>    [2]:
>    * physical cpu number must be equal to the vcpu number
>    * the total number of vcpus on a given host cannot exceed the numbers of
> physical cpus
>
> BTW: Our solution will reach the alpha state this month, if interested I
> might post it here.
>
> Cheers,
> Gyula
>
> ---
>
> [1] http://www.opennebula.org/documentation:rel1.4:oned_conf#hook_system
> [2] SMP overcommiting problem:
> http://www.mail-archive.com/kvm@vger.kernel.org/msg32079.html
> http://www.mail-archive.com/kvm@vger.kernel.org/msg33739.html. The route
> cause seems to be
> spin locks: they might cause dead locks in SMP systems when overcommitting
> host resources.
> The problem is also named "lock holder preemption", you might find related
> articles on the web,
> for instance:
> http://www.amd64.org/fileadmin/user_upload/pub/2008-Friebel-LHP-GI_OS.pdf.
> <
> http://www.reservoir-fp7.eu/index.php?mact=News,cntnt01,detail,0&cntnt01articleid=66&cntnt01returnid=108
> >
> ________________________________
> Feladó: users-bounces at lists.opennebula.org [
> users-bounces at lists.opennebula.org] ; meghatalmazó: Shi Jin [
> jinzishuai at gmail.com]
> Küldve: 2010. július 13. 1:28
> Címzett: opennebula user list
> Tárgy: [one-users] integrating cgroup into OpenNebula-KVM?
>
> Hi there,
>
> Redhat is going to include cgroups in the new RHEL-6, which is a great way
> to do quality of service (QoS) control on the resources, such as VM CPU,
> memory, network etc.
> Especially on CPU power, I remember the OpenNebula template has a variable
> CPU but it is not really used under KVM but rather a scheduling criteria.
> With cgroups, the CPU can have a meaning used to give each VM their proper
> share of the system computing power.
> I wonder if there is any plans to integrate this into OpenNebula.
>
> Thank you very much.
>
> --
> Shi Jin, Ph.D.
>
>


-- 
Shi Jin, Ph.D.
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