Virtualization In Your Hand

What virtualization technology will mean for the handset—and why systems engineers need to think about it.

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By Ed Sperling

The addition of multiple cores inside of computers has created an enormous opportunity for virtualization. Instead of running one operating system or one application, a single server or multicore PC can run multiple virtualized OSes on a single machine at the same time.

From the standpoint of energy efficiency, this has been a huge gain in data centers and the corporate enterprise. With most servers averaging 10% to 15% utilization, rather than the recommended 80%, one multicore serer running a virtualization layer could replace as many as eight less efficient single-core servers. That means less power to run applications, less power consumption by the new machines, and less power needed to cool server racks.

From an economic standpoint, this all makes sense. But that’s not the end of the road for virtualization. By the end of this year, that same technology will show up in smart phone prototypes, with products using this technology expected to hit the shelves in 2011.

“Our strategy has been that, over a period of time, mobile products would have a mobile interface,” said Srinivas Krishnamurti, director of product management and market development at VMware. “The goal is not just to shrink our existing technology to a mobile PC.”

Much of this has been under tight wraps since VMware bought Trango Virtual Processors in 2008. There has been much speculation in the mobile world about what all this means and how it will unfold, but little information. Details are now starting to emerge.

Krishnamurti said one use is allowing non-standard devices like the iPhone or Android device to be supported by corporate IT departments by using one of the cores for connecting to the enterprise. When that core is in use, access to other cores is restricted. But the next phases of development become far more interesting from a power-management standpoint.

Following the data center
Within the enterprise data center, one of the newer applications of virtualization technology is the ability to move processing onto machines, or even cores, that are underutilized and shut down any processors that are not in use. Entire regions of the data center can be shut down on weekends, for example, and loads concentrated where power is already being used. For a large company, that can result in savings of tens of millions of dollars annually.

In a mobile Internet device, that same strategy can be used to save battery. Lisa Su, senior vice president and general manager of Freescale’s networking and multimedia division, said the ability to partition for Linux and proprietary real-time operating systems opens up all sorts of possibilities for improving power management—particularly as more cores are added into the processors in these devices.

“Whatever we do at the infrastructure level will get down to the device level,” Su said. “We will see it on consumer devices soon.”

Taking full advantage of virtual machines in mobile Internet devices, however, requires that much of the power management be built into the software. A graphics-intensive application such as a game, for example, needs far more power than instant messaging. While those types of applications can be hard-wired into different sizes of cores with different voltages, allowing thyem to take advantage of whatever core becomes available with a virtual machine requires flexibility in the voltage supplied to the virtual machine running that application, regardless of what core it’s running on. There may be a fixed number of possibilities, or there may be a range of possibilities. So far, none of that has been fully worked out.

Also not fully worked out is how to verify the systems using this kind of technology. While virtualization has thrived in the enterprise, where machines are plugged into the power grid, handheld devices have had to rely on much more creative and painful techniques such as power gating, power islands and various on-off states. How virtualization will work with those states, and how devices will be verified, remains to be seen. For example, will virtualization supplant power islands altogether or be part of the strategy for turning parts of the chip on and off? And will virtualization ultimately require more power than power islands and right-sized cores with tightly coupled software?

Krishnamurti said VMware has been spending a lot of time on slimming down the hypervisor level in the virtualization layer, as well. The current layer for servers takes up about 32 megabytes of storage. In mobile phones, the new layer is expected to take up only 20 to 30 kilobytes. He declined to discuss more details, saying that VMware has a number of patents pending in this field.

“But from all the testing we’ve done so far, the power overhead is not significant,” he said. “The biggest drain on these devices is still the display.”