Saturday, May 18, 2013

Visualizing Go Benchmarks with benchviz

It's often useful to compare benchmark results between Go releases or your own programs. A new tool, benchviz, written in Go with the SVGo package, makes SVG visualizations designed to help you spot regressions and speedups and their magnitudes quickly.

Benchviz reads data from the benchcmp command, found in $GOROOT/misc/benchcmp, which produces output like this:

$ benchcmp old new
benchmark                 old ns/op    new ns/op    delta
BenchmarkBinaryTree17  131488202467 112637283111  -14.34%
BenchmarkFannkuch11     61976254131  61972329989   -0.01%
BenchmarkGobDecode        424145307    383073401   -9.68%
BenchmarkGobEncode        115032849    120332484   +4.61%
BenchmarkGzip           13868472766  13493855517   -2.70%

benchmark                  old MB/s     new MB/s  speedup
BenchmarkGobDecode             1.81         2.00    1.10x
BenchmarkGobEncode             6.67         6.38    0.96x
BenchmarkGzip                  1.40         1.44    1.03x
BenchmarkGunzip               11.23        11.55    1.03x

The benchcmp command produces two kinds of comparisons. "delta-style" shows the percent change between the measurements (negative numbers for going faster, positive numbers for slowdowns). The "speedup-style" shows how many times faster or slower the benchmarks are. Measurements less than 1.0 are considered performance regressions.

Benchviz supports two styles: the "bar" style draws a barchart-like view; regressions point to the left and speedups go to the right. The "inline" view shows portportionally-sized bars as "highlights" over the benchmark names. In both cases, colors indicate speedups or regressions.

If you add lines to the benchcmp output beginning with '#', benchviz will display these comment lines appropriately

Bars and inline styles

Two styles of speedup benchmarks

To install benchviz:

$ go install

You can run benchviz in a pipeline:

$ benchcmp old new | benchviz > bench.svg

or it can read from files:

$ benchviz linux-amd64-282dcbf1423.txt > linux.svg

Benchviz has options to control layout (overall width and height, top and left margins; the location and size of the bars; maximum speedup and delta) and style (bars or inline, colors, horizontal rules, single column data view)

$ benchviz -?
flag provided but not defined: -?
Usage of benchviz:
  -bh=20: bar height
  -col=false: show data in a single column
  -dm=100: maximum delta
  -h=768: height
  -left=100: left margin
  -line=false: show lines between entries
  -rcolor="red": regression color
  -scolor="green": speedup color
  -sm=10: maximum speedup
  -style="bar": set the style (bar or inline)
  -title="": title
  -top=50: top
  -vp=512: visualization point
  -vw=300: visual area width
  -w=1024: width

Thanks to Dave Cheney and Andrew Gerrand for feedback and encourgement.

No comments: