On Mon, 16 Mar 2015 16:05:37 +0100 Heinz Diehl htd+ml@fritha.org wrote:
On 09.03.2015, Martin Cigorraga wrote:
Just a minor clarification: when compiling, the -j flag should point to a unit above your available cores in order to fully utilize all of them.
Curious what would happen, I remembered this mail when compiling a new kernel today. A "nice -n 19 make -j" opened *hundreds* of cc incarnations, pushed the load to over 800 and seriously blocked the machine (an 8-core Xeon with 16 GB of RAM) within *seconds*!
Lucky you!
Are you using F21? Which kernel?
So, are you using rpmbuild with the src.rpm package, or compiling directly from the source tree?
What happens if you use -j 4? I would think you should get somewhere between 3 and 4 cores. The recommendation I saw to fully use all cores, were from cores+1 to cores*3. Cores*1.5 was a popular one, to allow for io slowness.
When I tried -j, I saw all the jobs queue, but only one core was used.
Thanks for reporting back.