Mark Haney wrote:
> Is there another way to use nice, or to fix that problem?  Or another
> way to manage CPU usage during an emerge?
> 

I'll just echo what Duncan said about nice / ionice.  However, you might 
find the impact of ionice -c 3 on compilation is reduced if you use a 
tmpfs for /var/tmp/portage.  Note that depending on what you're building 
you might need a fairly large tmpfs, and it could trigger swapping.

Note also that all your settings for niceness/etc won't impact RAM 
consumption - even a niced emerge is going to eat RAM when building some 
of the more massive packages.

However, I find that I can run almost anything with ionice -c 3 nice -n 
20 <command> and have almost no impact on my system at all.  Conversely, 
I set stuff like the mythtv backend to run with ionice -c 1 so that I 
never drop frames due to recording buffer issues.

Just don't go crazy with it.  If I try to build two copies of firefox 
(chroot and main) while running some java app that consumes 1GB of 
virtual address space, and then try to transcode a video or something 
while recording two videos, having all that stuff set to ionice/nice 
won't be of much help.