# Analyze system scalability with the Universal Scalability Law

This is an R package to analyze system performance data with the Universal Scalability Law.

The Universal Scalability Law (USL) was developed by Dr. Neil J. Gunther. It can be used to analyze system performance data in order to learn more about the scalability limitations of the system.

Details are presented in the book Guerrilla Capacity Planning and on the authors website.

## Example

Here is an example for the scalability analysis of a Sun SPARCcenter 2000 in the SPEC SDM 91 benchmark. The data used is available for download from the SPEC website and also included as a demo dataset.

library(usl)

# Load data from the SPEC SDM91 benchmark
data(specsdm91)

specsdm91

# Analyze "throughput" by "load" for the "specsdm91" data
usl.model <- usl(throughput ~ load, specsdm91)

# Show a model summary including scalability coefficients
summary(usl.model)

# Predict the location of the maximum in the scalability function
peak.scalability(usl.model)

# Plot original data and computed scalability function
plot(specsdm91, pch=16)

The summary command returns the following output:

Call:
usl(formula = throughput ~ load, data = specsdm91)

Scale Factor for normalization: 64.9

Efficiency:
Min     1Q Median     3Q    Max
0.1214 0.2254 0.3966 0.7799 1.0000

Residuals:
Min     1Q Median     3Q    Max
-70.89 -23.59  19.39  86.14 274.88

Coefficients:
Estimate Std. Error t value Pr(>|t|)
sigma 1.705e-02  3.318e-03   5.137  0.00365 **
kappa 7.892e-05  2.492e-05   3.167  0.02489 *
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 140.6 on 5 degrees of freedom
Multiple R-squared: 0.9624,  Adjusted R-squared: 0.9549

The following image shows the plotted output:

## Installation

The package is available from CRAN. Use the following command to install the package from the repository:

install.packages("usl")

## Documentation

In addition to the package documentation there is also a package vignette available. Install the package and use the following command to open the vignette:

vignette("usl")

The vignette is also available from CRAN: https://CRAN.R-project.org/package=usl/vignettes/usl.pdf