Re: [gentoo-dev] [OT] PORTAGE_NICENESS is not so nice...

[Tomasz Mloduchowski]

I *think* it should go to user mailing list, forums, or somewhere else
where it's not [OT].

On Mon, 2005-10-24 at 06:47 -0400, Dave Nebinger wrote:
> So I set PORTAGE_NICENESS to 19 in /etc/make.conf on my primary gentoo
>  desktop so I could do emerges in the background and still use my box...
> [...]
> So I'm starting to question how useful PORTAGE_NICENESS actually is...  If
>  the system is pegged under niceness 19 and 0, but 0 completes in 10 minutes,
>  why would PORTAGE_NICENESS benefit me in any way?
nice, renice, PORTAGE_NICENESS (they're all the same) affect the way
kernel allocates CPU resources for running processes. Under normal
operating conditions, nice'd processes will get less CPU time (with nice
-n 19 ~1% of nice -n 0) than remaining nice 0 desktop processes.

It is possible to run CPU intensive jobs with 98% of CPU time when
other, competing processes are "nice". Basically, kernel will get the
nice processes out of the way if something else wants the CPU (not
completely, look around kerneltrap.org to see how exactly it works in
different schedulers)

What probably happened in your case was you run out of RAM. Than, your
machine started to use VERY slow swap space to run applications from,
and it may render some RAM-hogs (kde, e17, gnome) unresponsive. If you
are running an memory limited box, you may consider getting rid of -pipe
from CFLAGS, and setting MAKEOPTS="-j1". No niceness would help if your
system is waiting for swap space accesses.

Or just buy more RAM. Modules are getting ridiculusly cheap compared to
prices from last two years. I'd consider extra 128-256M for each thread,
you use to emerge stuff from, sufficient. And with linux using memory
very efficiently, more won't hurt either (and will likely decrease
application startup times significantly).

Tomasz