A Fine-Grained Power Gating Control on Linux Monitoring Power Consumption of Processor Functional Units

Atsushi KOSHIBA  Motoki WADA  Ryuichi SAKAMOTO  Mikiko SATO  Tsubasa KOSAKA  Kimiyoshi USAMI  Hideharu AMANO  Masaaki KONDO  Hiroshi NAKAMURA  Mitaro NAMIKI  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E98-C   No.7   pp.559-568
Publication Date: 2015/07/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E98.C.559
Type of Manuscript: Special Section PAPER (Special Section on Low-Power and High-Speed Chips)
Category: 
Keyword: 
energy conservation,  power gating,  operating system,  Linux,  

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Summary: 
The authors have been researching on reducing the power consumption of microprocessors, and developed a low-power processor called “Geyser” by applying power gating (PG) function to the individual functional units of the processor. PG function on Geyser reduces the power consumption of functional units by shutting off the power voltage of idle units. However, the energy overhead of switching the supply voltage for units on and off causes power increases. The amount of the energy overhead varies with the behavior of each functional unit which is influenced by running application, and also with the core temperature. It is therefore necessary to switch the PG function itself on or off according to the state of the processor at runtime to reduce power consumption more effectively. In this paper, the authors propose a PG control method to take the power overhead into account by the operating system (OS). In the proposed method, for achieving much power reduction, the OS calculates the power consumption of each functional unit periodically and inhibits the PG function of the unit whose energy overhead is judged too high. The method was implemented in the Linux process scheduler and evaluated. The results show that the average power consumption of the functional units is reduced by up to 17.2%.