Re: Native compilation on Windows, was Re: Bootstrap Compilation Speed

[Eli Zaretskii]

> From: "H. Dieter Wilhelm" <dieter@duenenhof-wilhelm.de>
> Cc: emacs-devel@gnu.org
> Date: Sun, 30 Jan 2022 19:12:25 +0100
> 
> >> I'm curious about the hyperthreading potential on my 4 core Intel laptop
> >> for doing compilations. And checked Emacs-28.0.91 from Corwin with (setq
> >> native-comp-async-jobs-number 8) vs 4 jobs.  My init.el forces Emacs to
> >> compile over 200 .eln files and it took about 5'40" with 8 logical
> >> processors and 7'7" with 4 logical processors.
> >
> > How many execution units you actually have there?
> 
> I think you mean with "execution units" what the task manager calls
> "cores".  This computer has 4 cores and 8 logical processors as you can
> see in the attached image from it's task manager.

If all you have is 8 execution units, using them all for compilation
will indeed not show twice the speed as with 4 jobs, because the OS
needs some of the CPU resources to do its job.

I generally find the default of half the execution units used for
background native compilation as adequate: it lets me work in Emacs
with almost no visible slowdown while JIT compilation goes on.