Benchmarking your changes

When working on issues related to performance, it is important to provide a performance benchmark for your changes to assess whether or not your change has a performance impact. PDF.js provides tools to do this easily. Normally you would create a simple manifest file has a couple of PDF files you're trying to optimize and run it multiple times, e.g. benchmark.json:

[
  {
    "id": "tracemonkey-eq",
    "file": "pdfs/tracemonkey.pdf",
    "md5": "9a192d8b1a7dc652a19835f6f08098bd",
    "rounds": 50,
    "lastPage": 5,
    "type": "eq"
  }
]

Run the following commands to create a 'baseline' measurement (i.e., before you make your changes):

$ git checkout master
$ SKIP_BABEL=true gulp generic
$ cd test
$ node test.js --browserManifestFile=resources/browser_manifests/browser_manifest.json \
    --statsFile=stats/results/baseline.json --statsDelay=5000 \
    --manifestFile=benchmark.json

Then apply your changes and create a 'current' measurement (replace <feature-branch> with the name of your branch):

$ cd ..
$ git checkout <feature-branch>
$ SKIP_BABEL=true gulp generic
$ cd test
$ node test.js --browserManifestFile=resources/browser_manifests/browser_manifest.json \
    --statsFile=stats/results/current.json --statsDelay=5000 \
    --manifestFile=benchmark.json

Finally, you can compare the measurements and see any performance differences:

$ node stats/statcmp.js stats/results/baseline.json stats/results/current.json

As a sanity check, you should do this twice with the same code and compare the results.