Enable clang build timing analysis

I didn't enable this by default for clang due to making the build time
10% worse or so. Unfortunate, but tbh devs for whom 10% of build time is
not *that* bad should probably simply enable this.

Change-Id: I8d1e5b6f3f76c649a4e2f115f534f7f97cee46e6

1 files changed, 15 insertions, 0 deletions

diff --git a/doc/manual/rl-next-dev/build-timing-analysis.md b/doc/manual/rl-next-dev/build-timing-analysis.md
new file mode 100644
index 000000000..e59f3ca02
--- /dev/null
+++ b/doc/manual/rl-next-dev/build-timing-analysis.md
@@ -0,0 +1,15 @@
+---
+synopsis: Clang build timing analysis
+cls: 587
+---
+
+We now have Clang build profiling available, which generates Chrome
+tracing files for each compilation unit. To enable it, run `meson configure
+build -Dprofile-build=enabled` then rerun the compilation.
+
+If you want to make the build go faster, do a clang build with meson, then run
+`maintainers/buildtime_report.sh build`, then contemplate how to improve the
+build time.
+
+You can also look at individual object files' traces in
+<https://ui.perfetto.dev>.