Skip to content

PROFILING.md

Latest commit

 

History

History
75 lines (53 loc) · 2.07 KB

PROFILING.md

File metadata and controls

75 lines (53 loc) · 2.07 KB

Profiling

This repo includes a small Rust helper, oy-profile, to summarize samply/Firefox JSON profiles.

Record with samply

Build a release binary and record a profile:

cargo build -p oyo --release
samply record --save-only -o profile.json.gz -- ./target/release/oy --range HEAD...HEAD

Notes:

  • Use a .json.gz output name to keep files small.
  • If you need perf permissions on Linux:
sudo sysctl -w kernel.perf_event_paranoid=1

Reset it when you are done:

sudo sysctl -w kernel.perf_event_paranoid=2

Summarize profiles

Quick report (hot threads/paths/spots/modules):

cargo run -p oyo --bin oy-profile -- profile.json.gz --report --top 15

Add --verbose to include the full ranked function table with --report. By default the report includes idle samples (percent columns are total). To exclude idle samples (poll/sleep/etc), pass --no-idle. Customize the idle matcher with:

cargo run -p oyo --bin oy-profile -- profile.json.gz --report --no-idle
cargo run -p oyo --bin oy-profile -- profile.json.gz --report --idle-pattern "my_idle_fn"

List threads:

cargo run -p oyo --bin oy-profile -- profile.json.gz --list-threads

Pick a thread and mode (inclusive = hot paths, leaf = self time):

cargo run -p oyo --bin oy-profile -- profile.json.gz --thread 0 --mode inclusive
cargo run -p oyo --bin oy-profile -- profile.json.gz --thread oy --mode leaf --top 30

By default the tool selects the hottest thread (based on the chosen metric) and prints a short thread summary. Control the metric and summary size with:

cargo run -p oyo --bin oy-profile -- profile.json.gz --metric weight
cargo run -p oyo --bin oy-profile -- profile.json.gz --metric time --top-threads 0

Interpretation notes:

  • CPU% is per-thread (threadCPUDelta / thread lifetime), not whole-system CPU.
  • Short-lived threads can show near-100% CPU even with few samples.
  • If threadCPUDelta or timing data is missing, CPU% is omitted.

Debug logs

For diff UI debug logs (extent markers, navigation, etc.), see docs/DEBUG.md.