Reserve CPU cores for specific guests?

Reserve CPU cores for specific guests?

[Neil Aggarwal]

Hello:

I don't think there is a way to do this with KVM, but
I figured I would ask:

I want to be able to offer virtual private servers (VPSs)
to clients.  I am going to use KVM for it.

I would like to offer clients the option to buy either:
1. A VPS which allows CPUs to be overcommitted.
2. A VPS with a dedicated CPU core.

So, for example, if I have a six core opteron, I might
sell:
2 VPSs with a dedicated CPU core
6 VPSs which allow overcommitted CPUs

Since I need one core for the hypervisor, there would
need to be a way to say that it gets a dedicated core
plus the other 2 VPSs get a dedicated core.  That
leaves 3 pooled cores to serve the 6 VPSs that 
are allowed to overcommit.

Is there a way to set up a pooled set of cores
for a given list of VPSs?  

I think I may have to use separate physical machine
for the VPSs with dedicated cores and the ones with
overcommitted ones.

Thanks,
	Neil

--
Neil Aggarwal, (281)846-8957, http://www.JAMMConsulting.com
CentOS 5.4 KVM VPS $55/mo, no setup fee, no contract, dedicated 64bit CPU
1GB dedicated RAM, 40GB RAID storage, 500GB/mo premium BW, Zero downtime

Re: Reserve CPU cores for specific guests?

[Zdenek Kaspar]

Neil Aggarwal napsal(a):
> Hello:
> 
> I don't think there is a way to do this with KVM, but
> I figured I would ask:
> 
> I want to be able to offer virtual private servers (VPSs)
> to clients.  I am going to use KVM for it.
> 
> I would like to offer clients the option to buy either:
> 1. A VPS which allows CPUs to be overcommitted.
> 2. A VPS with a dedicated CPU core.
> 
> So, for example, if I have a six core opteron, I might
> sell:
> 2 VPSs with a dedicated CPU core
> 6 VPSs which allow overcommitted CPUs
> 
> Since I need one core for the hypervisor, there would
> need to be a way to say that it gets a dedicated core
> plus the other 2 VPSs get a dedicated core.  That
> leaves 3 pooled cores to serve the 6 VPSs that 
> are allowed to overcommit.
> 
> Is there a way to set up a pooled set of cores
> for a given list of VPSs?  
> 
> I think I may have to use separate physical machine
> for the VPSs with dedicated cores and the ones with
> overcommitted ones.
> 
> Thanks,
> 	Neil
> 
> --
> Neil Aggarwal, (281)846-8957, http://www.JAMMConsulting.com
> CentOS 5.4 KVM VPS $55/mo, no setup fee, no contract, dedicated 64bit CPU
> 1GB dedicated RAM, 40GB RAID storage, 500GB/mo premium BW, Zero downtime
> 
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

I think you can achieve that on some simple level DIY with taskset from
util-linux(-ng).

HTH, Z.

RE: Reserve CPU cores for specific guests?

[Neil Aggarwal]

> I think you can achieve that on some simple level DIY with 
> taskset from
> util-linux(-ng).

That is a good utility to know.  I did not know about that
earlier.  Thanks for the info.

I am wondering one thing though:

I will either need to call taskset when executing the
process or run taskset on a PID after it starts up.

Unless there is a way to tell KVM to call taskset when starting
a guest, I think that is going to be hard to automate since the
guests will get different PID each time they are started.

Any suggestions?

Thanks,
	Neil

--
Neil Aggarwal, (281)846-8957, http://www.JAMMConsulting.com
CentOS 5.4 KVM VPS $55/mo, no setup fee, no contract, dedicated 64bit CPU
1GB dedicated RAM, 40GB RAID storage, 500GB/mo premium BW, Zero downtime 

Re: Reserve CPU cores for specific guests?

[Thomas Fjellstrom]

On Sun November 8 2009, Neil Aggarwal wrote:
> > I think you can achieve that on some simple level DIY with
> > taskset from
> > util-linux(-ng).
> 
> That is a good utility to know.  I did not know about that
> earlier.  Thanks for the info.
> 
> I am wondering one thing though:
> 
> I will either need to call taskset when executing the
> process or run taskset on a PID after it starts up.
> 
> Unless there is a way to tell KVM to call taskset when starting
> a guest, I think that is going to be hard to automate since the
> guests will get different PID each time they are started.
> 
> Any suggestions?
>

None directly related, but libvirt's kvm support supports pinning a vm to a 
physical cpu. At least it has the option in virt-manager.

> Thanks,
> 	Neil
> 
> --
> Neil Aggarwal, (281)846-8957, http://www.JAMMConsulting.com
> CentOS 5.4 KVM VPS $55/mo, no setup fee, no contract, dedicated 64bit CPU
> 1GB dedicated RAM, 40GB RAID storage, 500GB/mo premium BW, Zero downtime
> 
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 


-- 
Thomas Fjellstrom
tfjellstrom@shaw.ca

RE: Reserve CPU cores for specific guests?

[Neil Aggarwal]

> None directly related, but libvirt's kvm support supports 
> pinning a vm to a 
> physical cpu. At least it has the option in virt-manager.

That is exactly what I needed.
My KVM host does not have a GUI so I have been using
virsh.  I did not notice that option before.

Thank you,
	Neil

--
Neil Aggarwal, (281)846-8957, http://www.JAMMConsulting.com
CentOS 5.4 KVM VPS $55/mo, no setup fee, no contract, dedicated 64bit CPU
1GB dedicated RAM, 40GB RAID storage, 500GB/mo premium BW, Zero downtime