[CMake] Does Makefile generated by CMake support make -jN?

[Raymond Wan]

Hi Chao,


On Wed, Jul 13, 2016 at 10:54 AM, Chaos Zhang <zcsd2012 at gmail.com> wrote:
> I was trying to compile my project using CMake, after CMake generated
> Makefile.
> I used `/usr/bin/time -v make` to make the Makefile,  got the result:
> 'Percent of CPU this job got: 96%'.
> Then i used `/usr/bin/time -v make -j8` to make the Makefile, the result of
> CPU used is  'Percent of CPU this job got: 648%'.
> So i wonder if Makefile generated by CMake support make -jN, BTW my CPU is
> I7-4790, and after i use 'cat /proc/cpuinfo', there are 8 processors.


I'm not sure what you are asking...

You ran make with -j 8 and you got a percentage greater than 96% ...
this implies that the Makefile does support -jN, doesn't it?  If you
got 96% both times, then I would say there's a problem.

Is what you're wondering why it is 648% and not 800%?  I think that
depends on the dependencies in your Makefile.  It's possible that some
of them depend on each other in such a way that 8 parallel threads is
not possible.

Also, I can't remember the value returned by /usr/bin/time -v, but I
guess 648% is the average and not maximum.  So, perhaps there are
parts within the Makefile that only one thread could be used and then
it gets averaged out?

Ray