[gentoo-user] Hoping someone can help explain distcc to me

[Paul Hartman]

Hi,

I have a fast desktop computer and a slow laptop. Both are ~amd64
Gentoo. After some of the recent discussions about Gentoo on slow
devices, I thought I'd dust off the laptop and try to bring it up to
date.

I'd like to use distcc to make the desktop do all the compiling during
emerges. I've never been able to get distcc working properly, or, at
least, I've never been able to get it working to the point where using
distcc is any faster than not using it at all.

Desktop: 192.168.0.100
Laptop: 192.168.0.107

My goal is to just don't use the laptop at all. Do all compiling on
the desktop. So far, while it appears to be working (some things are
being compiled on the desktop, a very insignificant amount -- CPU
usage on the desktop is basically 0% during emerges on the laptop),
compile times are no better than just compiling everything on the
laptop. The laptop still has 100% CPU activity during emerges. I
realize the laptop is still going to do work during emerges, but
thought at least distcc might be able to help offload most of the
heavy part (the compiling).

Both machines contain "distcc" in FEATURES. It's not using
-march=native. I've tried various -jN values with no real difference
in performance.

On the desktop, /etc/conf.d/distcc contains (among other things):
DISTCCD_OPTS="${DISTCCD_OPTS} --allow 192.168.0.0/24"
DISTCCD_OPTS="${DISTCCD_OPTS} --listen 192.168.0.100"

And /etc/distccd/hosts contains:
192.168.0.0/24

On the laptop, /etc/conf.d/distcc contains (among other things):
DISTCCD_OPTS="${DISTCCD_OPTS} --allow 192.168.0.0/24"
DISTCCD_OPTS="${DISTCCD_OPTS} --listen 192.168.0.107"

And /etc/distccd/hosts contains:
192.168.0.100

Does anyone know any tricks or can tell me if I'm doing something
wrong? How much of a speed-up should I realistically expect? Should
distcc be able to exploit the fast machine to the fullest of its
abilities?

Thanks