The Benefits of Event-Driven Energy Accounting in Power-Sensitive
Systems
Frank Bellosa, "The Benefits of Event-Driven Energy Accounting in
Power-Sensitive Systems, Proceedings of 9th ACM SIGOPS European Workshop,
Kolding, Denmark, September 2000,
[Abstract(english)]
[Full Paper (pdf), 60 kB]
Abstract:
A prerequisite of energy-aware scheduling is precise knowledge of any
activity inside the computer system. Embedded hardware monitors (e.g.,
processor performance counters) have proved to offer valuable information
in the field of performance analysis. The same approach can be applied to
investigate the energy usage patterns of individual threads. We use
information about active hardware units (e.g., integer/floating-point unit,
cache/memory interface) gathered by event counters to establish a
thread-specific energy accounting. The evaluation shows that the
correlation of events and energy values provides the necessary information
for energy-aware scheduling policies.
Our approach to OS-directed power management adds the energy usage pattern
to the runtime context of a thread. Depending on the field of application
we present two scenarios that benefit from applying energy usage patterns:
Workstations with passive cooling on the one hand and battery-powered
mobile systems on the other hand.
Energy-aware scheduling evaluates the energy usage of each thread and
throttles the system activity so that the scheduling goal is achieved.
In workstations we throttle the system if the average energy use exceeds a
predefined power-dissipation capacity. This makes a compact, noiseless and
affordable system design possible that meets sporadic yet high demands in
computing power. Nowadays, more and more mobile systems offer the features
of reducible clock speed and dynamic voltage scaling. Energy-aware
scheduling can employ these features to yield a longer battery life by
slowing down low-priority threads while preserving a certain quality of
service.