Mach Performance Improvements

Firefox Tooling Announcements
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Hi all, I wanted to share some of the performance optimizations for mach that have landed recently or are landing soon:

  • bug 1775197 reduced the overhead of mach’s initialization process by ~30%-50% (highly platform and command specific), which means that commands you invoke could begin executing up to a second sooner than before, which should make things feel much more responsive.

  • bug 2018327 sped up a pre-test step that verifies all test files are in the right place before tests start running. On Windows, this shaved ~13 seconds off the time between invoking ./mach test/./mach xpcshell-test and tests actually starting to run (~75% speedup). Minor (if any) improvement on Linux/macOS.

  • bug 2017746 (landing today) speeds up ./mach configure by adding caching to a taskcluster step that verifies you have up-to-date toolchains, which saves up to 10 seconds (~50% speedup) if none of the toolchain input files changed since the previous run. The most common scenario that benefits from this is editing your mozconfig then building.

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