NDLI: Efficient online computation of core speeds to maximize the throughput of thermally constrained multi-core processors

Content Provider	IEEE Xplore Digital Library
Author	Rao, R. Vrudhula, S.
Copyright Year	2008
Description	Author affiliation: Dept. of Comput. Sci. & Eng., Arizona State Univ., Tempe, AZ (Rao, R.; Vrudhula, S.)
Abstract	We address the problem of efficient online computation of the speeds of different cores of a multi-core processor to maximize the throughput (which is expressed as a weighted sum of the speeds), subject to an upper bound on the core temperatures. We first compute the solution for steady-state thermal conditions by solving a linear program. We then present two approaches to computing the transient speed curves for each core: (i) a local solution, which involves solving a linear program every time step (of about 10 ms), and (ii) a global solution, which computes the optimal speed curve over a large time window (of about 100 s) by solving a non-linear program. We showed that the local solution is insensitive to the weights assigned in the performance objective (hence the need for the global solution). This is because a reduction in the speed of a core can only reduce the temperature of the other cores over much larger time periods (of the order of several seconds). The local solution is then completely determined by the temperature constraint equations. We show that the constraint matrix exhibits a special property - it can be expressed as the sum of a diagonal matrix and a matrix with identical rows. This allows us to solve the multi-core thermal constraint equations analytically to determine the (temporally) local optimum speeds. Further, we showed that due to this property, the steady-state speed solution selects a set of threads to operate at maximum temperature, and turns off all unused cores. Hence, to ensure that all available threads are scheduled, we impose a ldquofairnessrdquo constraint. Finally, we show how the open-loop speed control methods proposed above could be used together with a feedback controller to achieve robustness to model uncertainty.
Starting Page	537
Ending Page	542
File Size	622468
Page Count	6
File Format	PDF
ISBN	9781424428199
ISSN	10923152
DOI	10.1109/ICCAD.2008.4681627
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2008-11-10
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Throughput Multicore processing Temperature Steady-state Equations Yarn Upper bound Velocity control Adaptive control Robust control
Content Type	Text
Resource Type	Article
Subject	Computer Graphics and Computer-Aided Design Computer Science Applications Software

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