ccache-distcc

The following instructions are for Debian and they might work for Ubuntu as well.

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Motivation

• If you don't use ccache you'll waste time.
• If you don't use distcc you'll waste time.
• If you don't use ccache and distcc together, you'll waste time.

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Some theory

You might want to use ccache and distcc all the time, even if you compile only from a single machine. This way, you can add nodes to the cluster anytime and the cache will be valid when you compile with a single processor some other time.

This is especially useful if you have a laptop.

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Installing

In the front-end machine:

 aptitude install ccache distcc gcc g++

In the nodes:

 aptitude install distgcc gcc g++

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Configuring ccache

The first thing to set is the maximum cache size. The more, the better. For me a few gigabytes are more than enough. If need to cache a few kernel compilations, it will be enough.

$ ccache --max-size 5G

You can check statistics anytime you like with ccache -s.

$ ccache -s
cache directory                     /home/galactus/.ccache
cache hit                              0
cache miss                             0
files in cache                     43454
cache size                         265.9 Mbytes
max cache size                       3.0 Gbytes

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Configuring distcc

In the compilation nodes, make sure that your computer is allowed to use distcc. To configure it use:

dpkg-reconfigure distcc

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The environment

In the front-end machine, you might want to use something like the following environment:

# When You're alone
# export DISTCC_HOSTS=localhost

# When you use the cluster
# Faster machines first.
export DISTCC_HOSTS="192.168.1.2 192.168.1.3 192.168.1.4 localhost"
export CCACHE_PREFIX="distcc"
#If you don't want to cache the compilation results
#export  CCACHE_DISABLE.  

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An example

This is an example of what you would need to do to use ccache with the Linux kernel.

--- Makefile.old        2007-05-30 10:07:00.000000000 -0500
+++ Makefile    2007-05-30 10:07:49.000000000 -0500
@@ -195,8 +195,8 @@
          else if [ -x /bin/bash ]; then echo /bin/bash; \
          else echo sh; fi ; fi)
 
-HOSTCC       = gcc
-HOSTCXX      = g++
+HOSTCC       = ccache gcc
+HOSTCXX      = ccache g++
 HOSTCFLAGS   = -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer
 HOSTCXXFLAGS = -O2
 
@@ -281,7 +281,7 @@
 
 AS             = $(CROSS_COMPILE)as
 LD             = $(CROSS_COMPILE)ld
-CC             = $(CROSS_COMPILE)gcc
+CC             = ccache $(CROSS_COMPILE)gcc
 CPP            = $(CC) -E
 AR             = $(CROSS_COMPILE)ar
 NM             = $(CROSS_COMPILE)nm

In this example, we used cross-compiler.

In order to use all the nodes in the cluster, you need to call make with the "-j" flag. For instance:

crossmake -j5 vmlinux