[OlivierLi]

Using some scripts/parsers to take DTrace/perf/Instruments/ETW data and transfer it to perfetto was one of the most exciting moments of my performance engineering career. It’s such a powerful thing compared to every single other workflow I’ve ever used.

It just shows contention in a way that so hard to see otherwise.

If this tool packages some of that in an easier to use package it’s going to be a great tool for some.

[protomolecule]

"It just shows contention in a way that so hard to see otherwise."

Could you elaborated on this? I've never used it myself.

[OlivierLi]

You start with a trace event you care about. You see it’s too slow. The first step is that you see explicitly that it’s not because the code is slow, you constantly get descheduled because there are thread state indicators above your event.

Then you navigate to the CPU tracks find the thread(s) that were running instead of the one you care about and directly inspect their stacks. Sometimes almost nothing is running. Maybe contention is not on even on the CPU.

So the “parsing styles was slow” conclusion you would get from only looking at histograms turns into “parsing styles was slow because I couldn’t get my fonts and that was slow because IndexDB was hogging the hard drive on another process”

Edit: I should mention the user provided trace events are very important here. You get flow arrows really underlining task posting and IPC response as well as user interactions. Entry/Exit style uprobes on function are great but I found won’t get you all the way there on a large application.

[protomolecule]

Thanks!

[Ygg2]

I'm curious how does it work on Windows?