at g2k23 we talked about this issue for a bit. The make(1) manual
page can be confusing because it says:
-j max_processes
Specify the maximum number of processes that make may have
running at any one time.
Nope, that's wrong. It can create vast number of processes including
their sub-processes upon pipelines, so it is very difficult to judge
what it will do.
We could fix it (with an ugly hack you don't want to hear about), but
then -j will probably end up way underutilizing cpus (because it would
count even your "sh" processes sitting idle), and then people would
probably start running -j 100 on 16 cpu machines and be right back
at the same underload vs overload situation.
> Peter Hessler:
>
> > This package takes quite a while to build, so I marked it as parallel to
> > use more CPUs.
>
> This appears inefficient. Right now, I have a gambit build sitting
> here, taking up five CPU slots...
>
> 5*lang/gambit(build) [29274] 26% frozen for 22mn
>
> ... but running only two cc(1) processes.
>
> 59060 p1 I+p 0:00.02 | `-- /usr/bin/make build
> 97813 p1 I+p 0:00.00 | `-- /bin/sh -ec lock=gambit-4.9.4p0;
> export
> 74087 p1 I+p 0:00.01 | `-- /usr/bin/make _internal-build
> 3321 p1 I+p 0:00.02 | `-- /usr/bin/make do-build
> 54023 p1 I+p 0:00.00 | `-- /bin/sh -ec ulimit -s 12288 &&
> cd
> 72554 p1 I+p 0:00.01 | `-- /usr/bin/make mkdir_p=mkdir -p
> -
> 21475 p1 I+p 0:00.01 | `-- /bin/sh -ec for subdir in
> incl
> 71313 p1 I+p 0:00.00 | `-- /bin/sh -ec for subdir in
> in
> 19391 p1 I+p 0:00.05 | `-- /usr/bin/make core
> 71280 p1 R+/10 26:59.87 | |-- /usr/bin/cc -B
> /usr/obj/
> 4319 p1 R+/9 26:47.57 | `-- /usr/bin/cc -B
> /usr/obj/
>
> --
> Christian "naddy" Weisgerber na...@mips.inka.de
>
