[gentoo-user] Limit number of cores used by emerge?

[Mark Knecht]

Hi,
   Is there a portage option that will limit the number of cores used
by emerge? For instance, in a chroot on a 12 core machine I want to
limit emerge to not using more than 3 cores?

   If possible, I'd also like to limit the total disk bandwidth
consumption during emerge. For instance, when untarring a big file to
do the emerge at times the disk consumption gets to high and the
machine becomes laggy. Is there an option that addresses this?

   These questions are mostly about being able to update a chroot
mid-day without other tasks slowing down too much. I don't care how
long the chroot really takes to get a huge emerge done, but rathe just
keeping the machine very responsive while it's happening. I already
use:

MAKEOPTS="-j3"
PORTAGE_NICENESS="15"

which helps (I think) but it doesn't totally address either of the issues above.

Thanks,
Mark