What does "CC Graph Reduction" in Firefox Performance tool mean?

Question

I am profiling a JavaScript application using the Firefox developer tools, specifically the Perfomance tab.

In the result I see the following entry:

CC Graph Reduction - ForgetSkippable

Unfortunately I cannot find a clear documentation explaining what it is.

I would like to know:

• What is it?
• When is this event usually fired?

Answer 1

According to the MDN documentation CC stands for "cycle collection". Some explanation on what cycle collection is can be found in a blog post of Kyle Huey. This post describes it like this:

The cycle collector is sort of like a garbage collector for C++.

And a garbage collector is used to detect objects in memory, which are not referenced. The memory holding those objects can then be freed.

Unfortunately there doesn't seem to be any explanation for the 'CC Graph Reduction' event and how it differs from the 'Cycle Collection' event. So, I've created a bug report asking to describe the different filters available within the Performance panel.

Update:

The 'CC Graph Reduction' event got described on the MDN page explaining the performance waterfall graph like this:

Preparation/pre-optimization for Cycle Collection.