On 24/01/2020 10:27, Jonathan Wakely wrote:
On Fri, 24 Jan 2020 at 03:39, Nicholas Krause <[email protected]> wrote:
Sorry for the second message Allan but make -j does not scale well
beyond 4 or
8 threads and that's considering a 4 core or 8 machine. The problem has to
do with large build machines with CPUs with more cores than this or as
is becoming
more common on mainstream systems.
And make scales well beyond 8 processes (not threads) on such machines.
The problem isn't make, per se, or even gcc. It's the build system as a
whole.
On a highly multi-core machine, gcc itself hits the bottle-neck called
configure. That's serial, run *many* times (especially when there are
many multilibs) and dominates build time.
On high multi-core machines, gcc's 15-minute system load gets no-where
near to the number of threads on the machine because of this.
R.
