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* (doi:10.1007/978-3-540-31010-5)
and on the authors
website.

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(throughput ~ load, specsdm91)
usl.model
# 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)
plot(usl.model, col="red", add=TRUE)
```

The `summary`

command returns the following output:

```
Call:
usl(formula = throughput ~ load, data = specsdm91)
Efficiency:
Min 1Q Median 3Q Max
0.0876 0.1626 0.2860 0.5624 0.7211
Residuals:
Min 1Q Median 3Q Max
-81.7 -48.3 -25.1 29.5 111.1
Coefficients:
Estimate Std. Error t value Pr(>|t|)
alpha 0.0277285 0.0091217 3.04 0.0384 *
beta 0.0001044 0.0000199 5.25 0.0063 **
gamma 89.9952330 14.2134894 6.33 0.0032 **
---
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
Residual standard error: 82.8 on 4 degrees of freedom
Scalability bounds:
limit: throughput 3246 (Amdahl's asymptote)
peak: throughput 1884 at load 96.52
opt: throughput 1542 at load 36.06
```

The following image shows the plotted output:

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

`install.packages("usl")`

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