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From: Rolf Campbell <Endlisnis AT mailc DOT net>
Subject: Re: parallel make
Date: Wed, 27 Aug 2003 20:15:19 -0400
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make -j does work in cygwin, to an extent.  If you try to use too many 
processes, cygwin seems to flip out.  -j20 does seem to work fine though 
(it only starts acting strang around -j100).

On my large build system, we have a slow disk, and I find that when the 
disk cache is empty, -j4 speeds it up about 40%.  When the build system 
is cached, -j slows things down by a few percent.  This is dealing with 
1 processor.  Of course, if you have multiple processors, the speed 
should scale linearly (with 4 cpu's, -j4 is about 70% faster).

Rich Elberger wrote:

> Hi folks,
> Currently our build environment uses parallel make (-j jobs option) on all
> our unixes using gnu tools.  We use an older version of gnu tools on our
> windows boxes.  The older make on the windows box does not do parallel
> make (or at least correctly).  I want to upgrade to the latest cygwin to
> see if parallel make works, but this will require significant changes to
> our build engine, so I would like to confirm a few things if possible.
> 
> 1. Does the -j jobs option work well on windows. (part b: does it work
> with the MSVC (6/7) compiler (which probably doesn't make a difference
> anyway)?
> 2. Has anyone done this in a very large project, and if so, do you have
> any performance gain stats (which, I acknowledge, is tied to
> processor-intensive makes and how many processors the machine has).
> 
> I realize that dos does not allow for threading so I don't know if this is
> a cmd.exe-related issue or not (since cmd.exe is the parent shell, I
> don't know if this affects the behavior).
> 
> thanks in advance --
> 
> 



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