getFlameGraphTiming is slow

STR:

• View this profile.
• Then change the time selection.
• It’s really slow.

Here is a recording of that slowness, with getFlameGraphTiming focused. https://perfht.ml/2p0EXzK

Specifically the call tree method getDisplayData is the culprit in being the most slow. The results are already cached, but I think we need to computer fewer things, or provide another avenue to get that data that isn’t so expensive.

[julienw]

Ah yes, thanks @brisad! Definitely you should use a simpler method instead of getDisplayData. In the profile’s inverted tree, extractFaviconFromLibname stands out right after getChildren so I think it’s a worthwhile optimization.

[julienw]

This is much much better than it was, but we can still feel a slowness sometimes. Is it good enough ?

I took a new profile: https://perfht.ml/2MDBUvf The most time is spent now in getFlameGraphTiming itself. I think it will be difficult to look further until we get the per-line information. Or maybe as I suggested in https://github.com/devtools-html/perf.html/issues/844#issuecomment-384451033 we could prefilter the nodes we want to display to cut down the algorithm time.