Improve JavaScript Performance Analysis Results With User Marks

When working on advanced
JavaScript code, like a 3D engine, you may ask yourself what you can do to optimize,
and how much time you should spend in some specific pieces of code. In this
tutorial, I will share several tools that provide insight into how your code is
performing, and show you how to make the most of user marks in the memory graph
to analyze your performance.

Can’t wait to see what this
tutorial is about? Watch this video:


Feel
free to ping me on Twitter (
@deltakosh) if you
want to discuss this article!

Need a Profiler?

One profiler that comes to mind is
the integrated profiler you can find using new updates to the Internet Explorer F12
Dev Tools
—enhancements that will also be available for Microsoft Edge. Of course, you can use
any similar tools you prefer too on your dev box. 

If you want to try this out
on Android, iOS, or Mac OS, you can also use remote.IE to get an instance of Windows 10 Technical preview running in minutes. Then
open the Internet Explorer “e” you’ve been avoiding (it is a temporary client
shell that has Project Spartan’s new rendering engine configured), hit F12 and now you can see what I’ll show you:

temporary client shell that has Project Spartans new rendering engine configured

Please note that with the
new F12 tools that we shipped with Windows 10 Technical preview, profiler is now part of
the UI responsiveness window:

profiler is now part of the UI responsiveness window

Let’s see other options
that can give you more insights about how your code is performing.

console.time

You just have to call console.time()
and console.timeEnd() around the piece of code you want to evaluate. The
result is a string in your console displaying the time elapsed between time
and timeEnd.

This is pretty basic and
can be easily emulated, but I found this function really straightforward to use.

Even more interesting,
you can specify a string to get a label for your measurement.

This is, for instance, what
I did for Babylon.js:

console.time("Active meshes evaluation");
this._evaluateActiveMeshes();
console.timeEnd("Active meshes evaluation");

This kind of code can be
found around all major features and then, when performance logging is enabled,
you can get really great information:

performance logging information

Be warned that
rendering text into the console can consume CPU power.

Even if this function is
not per se a standard function, the browser compatibility is pretty great.
Chrome, Firefox, IE, Opera and Safari support it.

Performance Object

If you want something
more visual, you can use the performance object as well. Among other interesting features to help you measure a
web page performance, you can find a function called mark that can emit
an user mark.

A user mark is the association
of a name with a time value. You can measure portions of code with this API in
order to get precise values. You can find a great article about this API by
Aurelio de Rosa on SitePoint too.

The idea today is to use
this API to visualize specific user marks on the UI Responsiveness screen:

UI Responsiveness screen

This tool allows you to
capture a session and analyze how the CPU is used:

capture a session and analyze how CPU is used

We can then zoom in on a
specific frame by selecting an entry called Animation frame callback and right-clicking on it to select filter to event.

The selected frame will
be filtered then:

selected frame filtered view

Thanks to the new F12
tool, you can then switch to JavaScript call stacks to get more details about what
happened during this event:

more details about what happened during this event

The main problem here is
that it is not easy to get how code is dispatched during the event.

And this is where user
marks enter the game
. We can add our own markers and then be able to
decompose a frame and see which feature is the more expensive and so on.

performance.mark("Begin of something…just now!");

Furthermore, when you
create your own framework, it is super handy to be able to instrument your code
with measurements:

performance.mark("Active meshes evaluation-Begin");
this._evaluateActiveMeshes();
performance.mark("Active meshes evaluation-End");
performance.measure("Active meshes evaluation", "Active meshes evaluation-Begin", "Active meshes evaluation-End");

Let’s see what you can
get with Babylon.js, for instance, with the “V8”
scene:

V8 scene in Babylonjs

You can ask Babylon.js
to emit user marks and measures for you by using Debug layer:

Screenshot of Debug layer function

Then, using the UI
responsiveness analyzer, you can get this screen:

UI responsiveness analyzer

You can see that user
marks are displayed on top of the event itself (the orange triangles) as well as
segments for every measure:

user marks displayed on top of the event

It is then super easy
to determine that, for instance, the [Render targets] and [Main render] phases are
the most expensive.

The complete code used by
Babylon.js to allow users to measure the performance of various features is
the following:

Tools._StartUserMark = function (counterName, condition) {
    if (typeof condition === "undefined") { condition = true; }
    if (!condition || !Tools._performance.mark) {
        return;
    }
    Tools._performance.mark(counterName + "-Begin");
};

Tools._EndUserMark = function (counterName, condition) {
    if (typeof condition === "undefined") { condition = true; }
    if (!condition || !Tools._performance.mark) {
        return;
    }
    Tools._performance.mark(counterName + "-End");
    Tools._performance.measure(counterName, counterName + "-Begin", counterName + "-End");
};

Tools._StartPerformanceConsole = function (counterName, condition) {
    if (typeof condition === "undefined") { condition = true; }
    if (!condition) {
        return;
    }

    Tools._StartUserMark(counterName, condition);

    if (console.time) {
        console.time(counterName);
    }
};

Tools._EndPerformanceConsole = function (counterName, condition) {
    if (typeof condition === "undefined") { condition = true; }
    if (!condition) {
        return;
    }

    Tools._EndUserMark(counterName, condition);

    if (console.time) {
        console.timeEnd(counterName);
    }
}; 

Thanks to F12 tools and user marks, you can
now get a great dashboard about how different pieces of your code are working
together.

More Hands-On With
JavaScript

It might surprise you a bit, but Microsoft
has a bunch of free learning on many open source JavaScript topics, and we’re on
a mission to create a lot more with Microsoft Edge coming. Check out my own:

Or our team’s learning series:

And some free tools: Visual Studio Community, Azure Trial, and cross-browser testing tools for Mac, Linux, or Windows.

This article is part of the web dev tech
series from Microsoft. We’re excited to share
Microsoft Edge and the new EdgeHTML rendering engine with you. Get free
virtual machines or test remotely on your Mac, iOS, Android, or Windows device
@
http://dev.modern.ie/.