Oracle VM 2.2 New Feature: CPU Scheduling Priority and Cap

One of the new features in Oracle VM 2.2 is the ability to set virtual CPU scheduling priority and cap per VM from Oracle VM Manager, which enables you to control access to CPU between multiple virtual machines to align with your IT/business priorities. With this enhancement, users can now control the Quality of Service (QoS) for CPU, network, and disk I/O through the intuitive Oracle VM Manager browser interface.

You log into Oracle VM Manager, then proceed to configure the VMs.


Scheduling Priority -- You can select High (100), Intermediate (50), or Low (1) priority for the virtual CPUs. You can also enter a custom priority by selecting Customize and entering a value out of 100 in the text area. If more than one virtual machine is running on the same managed node, use the Priority setting to give highest priority to one virtual machine, and less (or equal) priority to others. Priority levels determine which virtual machine is allowed to run first, in the event two or more are contending for the same physical processors. 

Scheduling Cap -- The cap optionally fixes the maximum amount (percentage) of CPU that can be consumed by the virtual machines, even if the host has idle CPU cycles. Use the cap to keep low priority virtual machines from consuming too many cycles on a node. You can select a High (100%), Intermediate (50%), or Low (10%) percentage of scheduled time for the virtual CPUs. You can also enter a custom percentage by selecting Customize and entering a percentage in the text area.

If you are using Oracle VM 2.1.2 or 2.1.5, you've had the I/O resource management features - setting bandwidth cap for each virtual network interface and prioritizing the virtual disks.

With network I/O traffic management, you can set bandwidth cap for each virtual network interface. All the virtual network interfaces (VIFs) share the physical network interface card (NIC) to communicate with the outside. If you have several VIFs, and you want to control how much bandwidth is granted to each VIF, you can configure the rate limit from Oracle VM Manager. The network traffic through the virtual network interface will not exceed the limit. The change will take effect without restart.


With storage I/O prioritization, you can also prioritize the virtual disk and enable disk priority, and select an appropriate priority class. The priority class ranges from 0 to 7. The priority class 0 has the highest priority, and 7 the lowest. Rather than being confined to a particular virtual machine, the priority of a virtual disk is global on the entire Oracle VM Server. Virtual disks of the same priority class take the same priority on the Oracle VM Server, even if they belong to different virtual machines.


CPU scheduling priority and cap along with I/O resource management features help assure that the CPU and I/O bandwidth usage are being used according to the priorities you want them to be. For more information about Oracle VM, please refer to the following resources:


Hi, the cpu capping is a very good start. Let me ask you one thing I've already asked at some oracle roadshow of last with little success. I had waited till the talk was over because it was a little off-topic, but the speaker, well, didn't know that much of oracle vm to understand what I mean. for service provider (and db hosting) scenarios it would be great to offer both capping and a "burstability", that means, a temporary, accountable allowing exceeding of the allocated ressources. i.e. your internet bandwidth might be guaranteed at 100Mbit/s and be burstable (if uplink has spare capacity and you haven't already been at that speed for days) to 200Mbit/s. This would allow a better (over?)provisioning of ressources and so on, but I'm yet to see someone thinking about it in Xen. I bet the big iron vm systems have it :)

Posted by darkfader on December 18, 2009 at 10:18 PM PST #

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