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Cryogenic: Enabling Power-Aware Applications on Linux

TitleCryogenic: Enabling Power-Aware Applications on Linux
Publication TypeThesis
Year of Publication2014
AuthorsMorales, A
AdvisorGrothoff, C
Academic DepartmentDepartment of Computer Science
DegreeM. Sc.
Number of Pages106
Date Published02/2014
UniversityTechnische Universitaet Muenchen
CityGarching bei Muenchen
Thesis TypeMasters
Keywordscooperative, cryogenic, GNUnet, Linux, POSIX, power

As a means of reducing power consumption, hardware devices are capable to enter into sleep-states that have low power consumption. Waking up from those states in order to return to work is typically a rather energy-intensive activity. Some existing applications have non-urgent tasks that currently force hardware to wake up needlessly or prevent it from going to sleep. It would be better if such non-urgent activities could be scheduled to execute when the respective devices are active
to maximize the duration of sleep-states. This requires cooperation between applications and the kernel in order to determine when the execution of a task will not be expensive in terms of power consumption.

This work presents the design and implementation of Cryogenic, a POSIX-compatible API that enables clustering tasks based on the hardware activity state. Specifically, Cryogenic's API allows applications to defer their execution until other tasks use the device they want to use. As a result,
two actions that contribute to reduce the device energy consumption are achieved: reduce the number of hardware wake-ups and maximize the idle periods.

The energy measurements enacted at the end of this thesis demonstrate that, for the specific setup and conditions present during our experimentation, Cryogenic is capable to achieve savings between 1% and 10% for a USB WiFi device.

Although we ideally target mobile platforms, Cryogenic has been developed by means a new Linux module that integrates with the existing POSIX event loop system calls. This allows to use Cryogenic on many different platforms as long as they use a GNU/Linux distribution as the main operating system. An evidence of this can be found in this thesis, where we demonstrate the power savings on a single-board computer.

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