Skip to content

Importing from custom sources

Jamie Wong edited this page Jan 22, 2019 · 2 revisions

speedscope supports two profiler-agnostic formats which are designed for use by tools which generate custom profiles: speedscope's own file format, and Brendan Gregg's collapsed stack format.

speedscope's file format

speedscope has a JSON-based file format. Its JSON schema can be found at

The file format is documented here: file-format-spec.ts.

An example profile can be found here: simple.speedscope.json.

If you author tools which generate this format, and speedscope should be able to import the result. This was e.g. the strategy used to add an output format for speedscope to rbspy. See rbspy/rbspy#161.

Brendan Gregg's collapsed stack format

If you want a simpler file format to generate and don't care about the units used for each stack, then Brendan Gregg's collapsed stack format is easy to generate and understand.

The format consists of one stack trace per line, with the line ending with a single integer indicating the weight of that sample. Semicolons separate stack frames in the stack trace.

Here's an example profile in that format:

main;a;b;c 1
main;a;b;c 1
main;a;b;d 4
main;a;b;c 3
main;a;b 5

A more realistic example can be found here: perf-vertex-stacks-01-collapsed-all.txt

Google "Trace Event Format"

Used in chrome://tracing, the Google "Trace Event Format" is JSON-encoded, event-based format for logging performance events. See for examples.

speedscope supports importing a subset of these events. Namely, it supports B, E, and X events, as well as the M events used to specify the names of processes and threads.

You can’t perform that action at this time.