I noticed that my processors were, in total, in use only about 50% of the time while making a Linux kernel.
I usually make the kernel, then make the modules.
I have just started a make bzImage in one terminal and a make modules in another and see that both my processors are in full use. I expect the total compile time will be a lot quicker as I'm compiling in parallel instead of serial.
Are there any "gotya's" that make this unsafe?
Just use
make -j 3
and it should compile in paralell, and will ensure any dependencies are properly handeled, this is the "official" way to do it.And no, you should not start building two objects in the same directory that are likely to try and compile the same code at the same time.