GNU make: should the number of jobs equal the number of CPU cores in a system?

Question

There seems to be some controversy on whether the number of jobs in GNU make is supposed to be equal to the number of cores, or if you can optimize the build time by adding

Answer 1

Both are not wrong. To be at peace with yourself and with author of software you're compiling (different multi-thread/single-thread restrictions apply at software level itself), I suggest you use:

make -j`nproc`

Notes: nproc is linux command that will return number of cores/threads(modern CPU) available on system. Placing it under ticks ` like above will pass the number to the make command.

Additional info: As someone mentioned, using all cores/threads to compile software can literally choke your box to near death (being unresponsive) and might even take longer than using less cores. As I seen one Slackware user here posted he had dual core CPU but still provided testing up to j 8, which stopped being different at j 2 (only 2 hardware cores that CPU can utilize). So, to avoid unresponsive box i suggest you run it like this:

make -j`nproc --ignore=2`

This will pass the output of nproc to make and subtract 2 cores from its result.