[Bug 264949] lang/gcc11: Needs build time warning for /tmp consumption

From: <bugzilla-noreply_at_freebsd.org>
Date: Thu, 30 Jun 2022 13:49:16 UTC

--- Comment #18 from Mark Millard <marklmi26-fbsd@yahoo.com> ---
(In reply to Lorenzo Salvadore from comment #16)

The FreeBSD port building servers use MAKE_JOBS_NUMBER=2 in
its make environment but LTO_BOOTSTRAP does not fully
respect that process count limit for its builder. If I
remember right, main-amd64 uses 14 builders. (No on-going
build so I can not check.) There is also how many threads
per process (at times anyway). MAKE_JOBS_NUMBER=2 is
visible in the logs.

Pretend, for the moment, that MAKE_JOBS_NUMBER=2 was fully
respected and only one thread per process. That would mean
28 processes on a system with 32 "freebsd cpus" (16
hyper-threaded cores). In this kind of context, building
lang/gcc1[1-3]* (so 5 ports) in separate builders at the
same time would take more like 8 hours elapsed than 40
hours elapsed. (I ignore that lang/gcc11* takes less time
than lang/gcc12* or lang/gcc13-devel [if I remember right].)

And other ports would also be built during those same 8+
hours: 23 other builders would be available and probably
be active much of the time.

Things are actually more complicated and I can not run such
a build on the system to see what would actually happen. But
it seems likely that less than 40 hours would elapse and other
ports would build over the time interval(s) that at least one
lang/gcc1[1-3]* builder was still active.

The general point would apply even if lang/gcc1[2-3]* took more
like 12+ hours but the detailed numbers would be different.

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