Comment by coldtea

Did you read the link we're discussing? It's in large part about why the slow startup times for Firefox's build scripts are a problem.

> Changing gears, my day job is maintaining Firefox's build system. We use Python heavily in the build system. And again, Python startup overhead is problematic. I don't have numbers offhand, but we invoke likely a few hundred Python processes as part of building Firefox. It should be several thousand. But, we've had to "hack" parts of the build system to "batch" certain build actions in single process invocations in order to avoid Python startup overhead. This undermines the ability of some build tools to formulate a reasonable understanding of the DAG and it causes a bit of pain for build system developers and makes it difficult to achieve "no-op" and fast incremental builds because we're always invoking certain Python processes because we've had to move DAG awareness out of the build backend and into Python. At some point, we'll likely replace Python code with Rust so the build system is more "pure" and easier to maintain and reason about.