Perfetto v57: fixing PyTorch traces, plus journald logs and an AI skill

We just released Perfetto v57 and I wanted to share the new things I’m most excited about. This is something I wanted to do for past releases but I just never quite got round to it. It’s also something I plan on doing more of going forward: there might even be dedicated pieces if I think the feature deserves it!

PyTorch traces reliably work!

What I’m most excited about in this release isn’t a feature but a bugfix. If you used the PyTorch profiler and opened the resulting trace in Perfetto, there was a decent chance some of your events would just not show up; specifically this would happen when these events overlapped each other on a single track.

Technically, PyTorch is in the wrong here. The Chrome Trace Event (JSON) format says duration events on a track have to nest and can’t overlap; if you need overlap, you’re supposed to use async events. chrome://tracing appears to handle them, but its rendering is actually buggy as soon as a trace has real overlaps; people just learned to live with it. So when a bug came in January about overlapping events being broken, I closed it as working-as-intended because I couldn’t see any easy fix from our end.