overhead,USL-method {usl} | R Documentation |
Overhead method for Universal Scalability Law models
Description
overhead
calculates the overhead in processing time for a system
modeled with the Universal Scalability Law.
It evaluates the regression function in the frame newdata
(which
defaults to model.frame(object)
). The result contains the ideal
processing time and the additional overhead caused by contention and
coherency delays.
Usage
## S4 method for signature 'USL'
overhead(object, newdata)
Arguments
object |
A USL model object for which the overhead will be calculated. |
newdata |
An optional data frame in which to look for variables with which to calculate the overhead. If omitted, the fitted values are used. |
Details
The calculated processing times are given as percentages of a non-parallelized workload. So for a non-parallelized workload the ideal processing time will always be given as 100% while the overhead for contention and coherency will always be zero.
Doubling the capacity will cut the ideal processing time in half but
increase the overhead percentages. The increase of the overhead depends on
the values of the parameters alpha
and beta
estimated by
usl
.
The calculation is based on A General Theory of Computational Scalability Based on Rational Functions, equation 26.
Value
overhead
produces a matrix of overhead percentages based on
a non-parallelized workload. The column ideal
contains the ideal
percentage of execution time. The columns contention
and
coherency
give the additional overhead percentage caused by
the respective effects.
References
Neil J. Gunther. Guerrilla Capacity Planning: A Tactical Approach to Planning for Highly Scalable Applications and Services. Springer, Heidelberg, Germany, 1st edition, 2007.
Neil J. Gunther. A General Theory of Computational Scalability
Based on Rational Functions. Computing Research Repository, 2008.
http://arxiv.org/abs/0808.1431
See Also
Examples
require(usl)
data(specsdm91)
## Print overhead in processing time for demo dataset
overhead(usl(throughput ~ load, specsdm91))