use of cpus in building

Michael David Crawford mdcrawford at
Sat May 28 17:20:46 PDT 2016

My tests find that its fastest to set the number of parallel builds to
1.5 to 2 times the number of cores.  I expect that's because some
tasks are CPU bound while other tasks are I/O bound.

In principle, you can get one of each kind going at the same time.
The I/O bound task doesn't use up much of the core's capacity.
Michael David Crawford, Baritone
mdcrawford at

      One Must Not Trifle With Wizards For It Makes Us Soggy And Hard To Light.

On Sat, May 28, 2016 at 11:07 AM, Ryan Schmidt <ryandesign at> wrote:
> On May 27, 2016, at 4:05 PM, Adam Dershowitz wrote:
>> On May 27, 2016, at 1:47 PM, Ryan Schmidt wrote:
>>> On May 25, 2016, at 5:07 PM, Justin C. Walker wrote:
>>>> On May 25, 2016, at 14:42 , Adam Dershowitz wrote:
>>>>> You can also manually change it for a single install, for example by using Such as:
>>>>> sudo port install port_whatever_name
>>>>> and then, for that specific install it will attempt to use 4 cores.  This can be handy to reduce the number of cores used, from the default, so that you can do other things on the machine while building.
>>> Instead, consider changing buildnicevalue in macports.conf from 0 to a greater number, up to 20. When MacPorts is configured to be "nice" it means that if other programs running on your computer need CPU time, they'll get it first.
>> Can this also be done on the command line for a specific install, instead of changing the config file?
> It's difficult to tell, because the nice value is not recorded in the log anywhere. If it does work, you would do it with:
> sudo port install whatever build.nice=20
> However, I don't see a downside to setting buildnicevalue in macports.conf. If your computer isn't doing anything else, MacPorts gets the CPU time. If your computer is doing something else, that something else gets the CPU time.
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