Perf instrumentation

[chriseppstein]

Instrument eyeglass and broccoli-eyeglass for performance metrics gathering with heimdalljs.

This introduces metrics collections for the following:

Always enabled

• eyeglass:broccoli:build:compileTree:<directory> - Each broccoli tree that gets compiled by broccoli-eyeglass.
  • Additional Metrics collected per tree:
  • cacheMissCount - how many sass files had to be recompiled
  • cacheHitCount- how many sass files were cached
  • numSassFiles - the number of sass files.
  • nodeSassTime - The time node-sass reports spending on compilation (includes waiting in the libuv worker queue).
  • importCount - The number of @import statements encountered.
  • uniqueImportCount - The number of @import statements that couldn't be deduplicated.
  • eyeglass:broccoli:build:invalidation - the cost of invalidating cache results based on what's changed since the last build.
• eyeglass:instantiation - The cost of instantiation and module creation.
  • eyeglass:modules - eyeglass modules creation during instantiation
  • eyeglass:modules:discovery - discovery of eyeglass modules within npm modules.
  • eyeglass:modules:resolution - resolving transitive eyeglass modules into a single version.

Conditionally enabled

When the environment variable EYEGLASS_PERF_DEBUGGING is set to a non-empty string additional perf metrics are collected. These incur performance overhead and can bloat the heimdall data returned.

Heimdall nodes are added for:

• eyeglass:import:module - the cost of module import (most imports are these)
  • eyeglass:import:assets - the cost of asset importing (delegated from the module importer)
  • eyeglass:import:fs - the cost of fs importing (delegated from the asset importer)

A heimdall monitor named sassFns is enabled causing stats to be collected against the broccoli-eyeglass tree node:

• The key is the sass function name that was invoked and the value is an object with a count and a time similar to how the heimdall fs monitor works. these times are collected with nanosecond precision. This only monitors sass functions implemented in js.