Thursday, April 08, 2010

Greening mutlicore computers

Greetings from the ANU in Canberra where PhD student Xi Yang is giving a seminar on how to use software to save power used by adding a low power cores to a computer architecture. He argues that around 2000 CPU chip designers could no longer increase performance by simply increasing the frequency the chip operated at. Instead designers included multiple cores on the one chip. Normally multiple cores of the same core designs are used. However, a better result might be obtained by using low power cores for routine tasks. The simplest example is a chip with one large core and one small core. The small core then handles routine tasks, such as slow input/output, freeing the big core for handling high performance application processing.

This technique seems to me to have considerable potential. Apart from increasing the performance of a system, it could be used to reduce the energy consumption. I use a netbook with a low power Intel Atom processor. This is more than adequate for routine web browsing, email and word processing, but is not sufficient for large application tasks. Having a high performance core would allow for occasional large tasks.

From a practical point of view a small low power processor is all most desktop computer users need. However, they will buy a higher performance unit just in case they need it. This computer will then waste energy by running idle most of the time. If they could buy a computer with a low power and high power core that would save energy, as the high power core would be unused most of the time.

Some desktop computers and laptops already include an ancillary low power chip, but this is only used to boot the computer using a stripped down operating system (usually a version of Linux or Windows CE) for quick casual browsing. The ancillary chip is unused when the main processor is active. It may be feasible to reprogram one of these systems to provide for both processors working at once. A might be to use several low power cores in place of the high performance core. As an example, eight Intel Atom cores might be provided, but normally only one would be used.

Seminar Details

OS-assisting Core: Improving the Power efficiency of Single ISA Asymmetric Chip

Xi Yang (School of Computer Science, CECS ANU)

CS HDR MONITORING CompSys Research Group

DATE: 2010-04-08
TIME: 10:45:00 - 11:15:00
LOCATION: Ian Ross Seminar Room

The power efficiency of asymmetric multicore systems can be improved by executing suitable operating system workload on low power cores. Devices interrupt handling, IO processing, scheduler and background kernel threads are suitable candidate workload.

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