Thankfully, eytzinger-ordered 4-ary trees work totally fine at 165+ fps, even at 3+ billion functions, but I like to read back through that post once in a while just in case I hit that perf wall someday.
Working on timestamp delta-compression at the moment to pack events into much smaller spaces, and hopefully get to 10 billion in 128 GB RAM sometime soon (at least for native builds of Spall).
Thanks for the kick to keep on pushing!
The other tool I didn’t mention is WinDbg. In my opinion, it’s the greatest debugger on any platform.
Missing out on one of the most useful areas for tracing which is time travel debugging. There are a number of interesting solutions there taking advantage of hardware trace, instrumentation, and deterministic replay. Even better when you get full visualization integration so you can do something like zoom in from a multiple minute trace onto a suspicious 200 ns function and then double click on it which will then backstep to that exact point in your program with the full reconstruction of memory at that time so you can debug from that point.
I just read your post and don't think it would take much to integrate with some of the visualisations you posted about, as a first step.
We've played around in the past with a sampling profiler (code here, requires a copy of our product to be useful though it could easily port to rr): https://github.com/undoio/addons/tree/master/sample_function... which can output in a format understood by Brendan Gregg's flame frames (https://www.brendangregg.com/flamegraphs.html)
But that's not quite the kind of tracing you're talking about. We also built a printf-style interface to our recording files, which seems closer: https://docs.undo.io/PostFailureLogging.html
Something like that but outputting trace events that can be consumed by Perfetto (say) would not be so hard to add. If we considered modifying the core record/replay engine then even more powerful things become possible.
No particularly good publicly visible documentation of the functionality, but it does that and is a publicly purchasable product.
They also had TimeMachine + PathAnalyzer from the early 2000s which was a time travel debug with visualization solution, but they were only about as integrated as most of the solutions you see floating around today.
is this something like https://www.reddit.com/r/ruby/comments/15o9hc1/timetraveling... ?
But Time Travel Debugging applies that to everything in the program, not just log statements - all function calls, variables, memory locations, etc can be reconstructed after the fact without having to log them explicitly.
Wow. This is some great engineering. Obviously that's what you'd do, but I'd never think of it in a thousand years!
p.s. I think the blog post could use more screengrabs of the traces. Great first pass at it though, and screengrabs can be added over time!
If anyone has any tips on how to trace JavaScript (not just profile by time, but deterministically measure the cost of it in CI), I'd love to hear tips!
