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via Nic Jansma

Licensed under the MIT license


Takes a .cpuprofile and determines the amount of time that was spent in or under (inclusive) a configurable list of source files.

As an example use case, cpuprofile-filter can be used to determine how much work a first- or third-party library is doing during page load.


Releases are available for download from GitHub.


cpuprofile-filter is available as the npm cpuprofile-filter module. You can install it using Node Package Manager (npm):

npm install cpuprofile-filter


Given a .cpuprofile input (JSON), cpuprofile-filter will analyze all of the stacks in the profile and calculate statistics such as how long the profile was captured for, total CPU time, idle CPU time, and the inclusive CPU time that was spent in the list of target files.

// import
var CpuProfileFilter = require("cpuprofile-filter");
// filter a profile
var results = CpuProfileFilter.filter(profile, config);
// filtered CPU time
var time = results.cpuTimeFiltered;

For example, you could specify a configuration of:

CpuProfileFilter.filter(profile, {
    "files": [

And cpuprofile-filter will return the amount of time (in microseconds) that were spent in any function of a.js, and, any work done (in any other function or file) triggered by a function in a.js.

cpuprofile-filter can optionally be given a list of functions to ignore.

For example, you could specify that you want to track anything in a.js except for calls to wrapper() in a.js:

CpuProfileFilter.filter(profile, {
    "files": [
    "ignore": [
            "functionName": "wrapper"

For the above example, note that as long as there is a second or more function in a.js besides wrapper() on the call stack, the sample will still be counted.


CpuProfileFilter.filter(profile, config)

Filters a .cpuprofile against the given config


  • profile: .cpuprofile data (in JSON)
  • config
  • config.files: A list of file names to filter
  • config.ignore: A list of ignores
  • config.ignore.functionName: A function name to ignore

Returns: An object with the following properties

    startTime: 1000,        // start time (microseconds)
    endTime: 2000,          // end time (microseconds)
    duration: 1000,         // duration (microseconds)
    sampleCount: 10,        // number of samples
    timePerSample: 100,     // time per sample (microseconds)
    cpuTime: 1000,          // CPU time of the entire profile (microseconds)
    cpuTimeFiltered: 500,   // CPU time of the filtered functions (microseconds)
    idleTime: 0             // Idle time (microseconds)


Tests are provided in the test/ directory, and can be run via mocha:

mocha test/*

Or via gulp:

gulp test

Version History

  • v1.0.0 - 2017-09-13: Initial version