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Diffstat (limited to 'third_party/libwebrtc/build/docs/debugging_slow_builds.md')
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diff --git a/third_party/libwebrtc/build/docs/debugging_slow_builds.md b/third_party/libwebrtc/build/docs/debugging_slow_builds.md new file mode 100644 index 0000000000..315690c32f --- /dev/null +++ b/third_party/libwebrtc/build/docs/debugging_slow_builds.md @@ -0,0 +1,19 @@ +# Debugging slow builds + +Some tips for debugging slow build times: +* Use [ninjatracing](https://github.com/nico/ninjatracing) and chrome:tracing to + view a timeline of the most recent build. + * Many bots output a build trace (look for a `"ninja_log"` link). +* Use `gn gen --tracelog trace.json` to create a similar trace for `gn gen`. +* Depot Tool's `autoninja` has logic for summarizing slow steps. Enable it via: + * `NINJA_SUMMARIZE_BUILD=1 autoninja -C out/Debug my_target` +* Many Android templates make use of + [`md5_check.py`](https://cs.chromium.org/chromium/src/build/android/gyp/util/md5_check.py) + to optimize incremental builds. + * Set `PRINT_BUILD_EXPLANATIONS=1` to have these commands log which inputs + changed. +* If you suspect files are being rebuilt unnecessarily during incremental + builds: + * Use `ninja -n -d explain` to figure out why ninja thinks a target is dirty. + * Ensure actions are taking advantage of ninja's `restat=1` feature by not + updating timestamps on outputs when their content does not change. |