Idleness is not sloth

Richard Golding, Peter Bosch,
Carl Staelin, Tim Sullivan, and John Wilkes
Hewlett-Packard Laboratories, Palo Alto, CA


Many people have observed that computer systems
spend much of their time idle, and various schemes
have been proposed to use this idle time productively.
The commonest approach is to off-load activity from
busy periods to less-busy ones in order to improve
system responsiveness. In addition, speculative work
can be performed in idle periods in the hopes that it
will be needed later at times of higher utilization, or
non-renewable resource like battery power can be
conserved by disabling unused resources.

We found opportunities to exploit idle time in our work
on storage systems, and after a few attempts to tackle
specific instances of it in ad hoc ways, began to investigate
general mechanisms that could be applied to this problem.
Our results include a taxonomy of idle-time detection algorithms,
metrics for evaluating them, and an evaluation of a number
of idleness predictors that we generated from our taxonomy.

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