Re: GCC Multi-Threading Ideas

["Richard Earnshaw (lists)" <Richard dot Earnshaw at arm dot com>]

On 24/01/2020 10:27, Jonathan Wakely wrote:
> On Fri, 24 Jan 2020 at 03:39, Nicholas Krause <xerofoify@gmail.com> 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.