Y axis = stack depth
X axis = percent of time spent in this function
If a function sits atop another, it was in its callchain and spent time in the callee. The more of a parent that is covered by the things it calls, the less it is doing and the more its children are doing.
This means the two main things (in my experience) to look for are:
- plateaus -- functions where a lot of time was spent
- shallow-sloped pyramids -- functions where time was spent up and down the callchain vs any isolated place
In the middle of the wide section you can see a function called "parseGif" which is where we'll focus. This particular flame graph was generated to analyze something inside there -- for the most part I don't care about the rest right now.