From 21921cfd73b7240c04a9319b4e059080c051a8f5 Mon Sep 17 00:00:00 2001
From: Martin von Zweigbergk <martinvonz@google.com>
Date: Wed, 13 Sep 2023 22:16:20 -0700
Subject: [PATCH] docs: add a section about profiling

---
 docs/contributing.md | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/docs/contributing.md b/docs/contributing.md
index 239c06723..b3c8cd91d 100644
--- a/docs/contributing.md
+++ b/docs/contributing.md
@@ -320,3 +320,21 @@ you can submit a PR based on the `gh-pages` branch of
 
  The `.rs` files generated from `.proto` files are included in the repository,
  and there is a GitHub CI check that will complain if they do not match.
+
+## Profiling
+
+One easy-to-use sampling profiler
+is [samply](https://github.com/mstange/samply). For example:
+```shell
+cargo install samply
+samply record jj diff
+```
+Then just open the link it prints.
+
+Another option is to use the instrumentation we've added manually (using
+`tracing::instrument`) in various places. For example:
+```shell
+JJ_TRACE=/tmp/trace.json jj diff
+```
+Then go to `https://ui.perfetto.dev/` in Chrome and load `/tmp/trace.json` from
+there.