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SBT Plugin

The SBT plugin allows users to warm up the compiler before measuring compilation times and analyzing statistics. This plugin is simple in its goals and bundles a set of tips that users of this plugin must take into account to get reliable data.

Installation

Add the plugin into project/plugins.sbt:

addSbtPlugin("ch.epfl.scala" % "sbt-scalac-profiling" % "1.1.2")

Usage

Run the profilingWarmupCompiler task in SBT in your CI / local machine before actually performing compilation to gather the data to build graphs. The default warmup duration is 60 seconds. You can modify it like this:

// setting the warmup duration to 30 globally
+ Global / profilingWarmupDuration := 30
// or setting the warmup duration to 50 in one project
val myProject = project.settings(
+ profilingWarmupDuration := 50
)

Several tips

To get reliable and predictable data, your infrastructure needs to be stable. These are some encouraged practices:

  1. The cpu load of the running machine must be kept low. Remove unnecessary processes and cron jobs that may be running on the background.
  2. Enable the -Vstatistics option before warming up the compiler. Otherwise, the warm-up will trigger JVM to decompile code and throw away optimized code. The same applies for other flags/build changes that affect compilation.
  3. Do not reload the SBT shell, or you'll need to warm up the compiler again.
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