ICECREAM(7)						      Icecream User's Manual						       ICECREAM(7)

NAME

       Icecream - A distributed compile system

DESCRIPTION

       Icecream is a distributed compile system for C and C++.

       Icecream  is created by SUSE and is based on ideas and code by distcc. Like distcc it takes compile jobs from your (KDE) build and distrib-
       utes it to remote machines allowing a parallel build on several machines you've got. But unlike distcc Icecream uses a central server  that
       schedules  the  compile	jobs  to  the  fastest free server and is as this dynamic. This advantage pays off mostly for shared computers, if
       you're the only user on x machines, you have full control over them anyway.

HOW TO USE ICECREAM

       You need:

       o  One machine that runs the scheduler ("./scheduler -d")

       o  Many machines that run the daemon ("./iceccd -d")

       If you want to compile using icecream, make sure $prefix/bin is the first first	entry  in  your  path,	e.g.  type  export  PATH=/opt/ice-
       cream/bin:$PATH (Hint: put this in ~/.bashrc or /etc/profile to not have to type it in everytime)

       Then  you  just	compile  with  make -j <num>, where <num> is the amount of jobs you want to compile in parallel. Don't exaggerate. Numbers
       greater than 15 normally cause trouble.

       WARNING: Never use icecream in untrusted environments. Run the deamons and the scheduler as unpriviliged user in such networks if you  have
       to! But you will have to rely on homogeneous networks then (see below).

       If you want funny stats, you might want to run "icemon".

USING ICECREAM IN HETEROGENEOUS ENVIRONMENTS

       If  you	are running icecream daemons (note: they _all_ must be running as root. In the future icecream might gain the ability to know when
       machines can't accept a different env, but for now it is all or nothing ) in the same icecream network but on  machines	with  incompatible
       compiler  versions you have to tell icecream which environment you are using. Use icecc --build-native to create an archive file containing
       all   the   files   necessary   to   setup   the   compiler   environment.   The   file	 will	have   a   random   unique    name    like
       "ddaea39ca1a7c88522b185eca04da2d8.tar.bz2"   per   default.   Rename   it   to	something  more  expressive  for  your	convenience,  e.g.
       "i386-3.3.1.tar.bz2". Set ICECC_VERSION=<filename_of_archive_containing_your_environment> in the shell environment where you start the com-
       pile  jobs  and	the file will be transfered to the daemons where your compile jobs run and installed to a chroot environment for executing
       the compile jobs in the environment fitting to the environment of the client. This requires that the icecream deamon runs as root.

       If you do not set ICECC_VERSION, the client will use a tar ball provided by the daemon running on the same machine. So you  can	always	be
       sure you're not tricked by incompatible gcc versions - and you can share your computer with users of other distributions (or different ver-
       sions of your beloved SUSE Linux :)

CROSS-COMPILING USING ICECREAM
       SUSE got quite some good machines not having a processor from Intel or AMD, so icecream is pretty good in using cross-compiler environments
       similiar  to  the  above  way of spreading compilers. There the ICECC_VERSION varaible looks like <native_filename>(,<platform>:<cross_com-
       piler_filename>)*, for example like this: /work/9.1-i386.tar.bz2,ia64:/work/9.1-cross-ia64.tar.bz2

       How to package such a cross compiler is pretty straightforward if you look what's inside the tarballs generated by icecc --build-native.

CROSS-COMPILING FOR EMBEDDED TARGETS USING ICECREAM
       When building for embedded targets like ARM often you'll have a toolchain that runs on your host and produces code for the target. In these
       situations you can exploit the power of icecream as well.

       Create  symlinks  from where icecc is to the name of your cross compilers (e.g. arm-linux-g++ and arm-linux-gcc), make sure that these sym-
       links are in the path and before the path of your toolchain, with $ICECC_CC and $ICECC_CXX you need to tell icecream which compilers to use
       for preprocessing and local compiling. e.g. set it to ICECC_CC=arm-linux-gcc and ICECC_CXX=arm-linux-g++.

       As the next step you need to create a .tar.bz2 of your cross compiler, check the result of build-native to see what needs to be present.

       Finally one needs to set ICECC_VERSION and point it to the tar.bz2 you've created. When you start compiling your toolchain will be used.

       NOTE: with ICECC_VERSION you point out on which platforms your toolchain runs, you do not indicate for which target code will be generated.

HOW TO COMBINE ICECREAM WITH CCACHE

       The  easiest  way  to use ccache with icecream is putting the symlink masquerades into /opt/icream/bin and putting small wrapper scripts in
       /opt/ccache/bin

	       cat /opt/ccache/bin/g++:

	       #! /bin/sh

	       export CCACHE_PATH=/opt/icecream/bin
	       export PATH=/opt/icecream/bin:/usr/bin:$PATH
	       ccache g++ "$@"

       Then you can replace /opt/icecream/bin with /opt/ccache/bin in your $PATH and all icecream calls will go through ccache (and Qt	will  com-
       pile in 62s :)

       Note  however  that  ccache isn't really worth the trouble if you're not recompiling your KDE three times a day from scratch (it adds quite
       some overhead in comparing the preprocessor output and uses quite some disc space and I found a cache hit of 18% a bit too few, so  I  dis-
       abled it again).

DEBUG OUTPUT

       You can use the environment variable ICECC_DEBUG to control if icecream gives debug output or not. Set it to debug to get debug output. The
       other possible values are error, warning and info (the -v option for daemon and scheduler raise the level per -v on the command line  -	so
       use -vvv for full debug).

SOME NUMBERS

       Numbers of my test case (some STL C++ genetic algorithm)

       o  g++ on my machine: 1.6s

       o  g++ on fast machine: 1.1s

       o  icecream using my machine as remote machine: 1.9s

       o  icecream using fast machine: 1.8s

       The  icecream  overhead	is  quite  huge as you might notice, but the compiler can't interleave preprocessing with compilation and the file
       needs to be read/written once more and in between the file is transfered.

       But even if the other computer is faster, using g++ on my local machine is faster. If you're (for whatever reason) alone in your network at
       some  point, you loose all advantages of distributed compiling and only add the overhead. So icecream got a special case for local compila-
       tions (the same special meaning that localhost got within $DISTCC_HOSTS). This makes compiling on my machine using icecream  down  to  1.7s
       (the overhead is actually less than 0.1s in average).

       As the scheduler is aware of that meaning, it will prefer your own computer if it's free and got not less than 70% of the fastest available
       computer.

       Keep in mind, that this affects only the first compile job, the second one is distributed anyway. So if I had to compile two of my files, I
       would get

       o  g++ -j1 on my machine: 3.2s

       o  g++ -j1 on the fast machine: 2.2s

       o  using icecream -j2 on my machine: max(1.7,1.8)=1.8s

       o  (using icecream -j2 on the other machine: max(1.1,1.8)=1.8s)

       The  math is a bit tricky and depends a lot on the current state of the compilation network, but make sure you're not blindly assuming make
       -j2 halfs your compilation time.

WHAT IS THE BEST ENVIRONMENT FOR ICECREAM

       In most requirements icecream isn't special, e.g. it doesn't matter what distributed compile system you use, you won't  have  fun  if  your
       nodes are connected through than less or equal to 10MBit. Note that icecream compresses input and output files (using lzo), so you can calc
       with ~1MBit per compile job - i.e more than make -j10 won't be possible without delays.

       Remember that more machines are only good if you can use massive parallelization, but you will for sure get the best result if your submit-
       ting  machine  (the one you called g++ on) will be fast enough to feed the others. Especially if your project consists of many easy to com-
       pile files, the preprocessing and file IO will be job enough to need a quick machine.

       The scheduler will try to give you the fastest machines available, so even if you add old machines, they will be used only  in  exceptional
       situations,  but  still	you  can  have	bad luck - the scheduler doesn't know how long a job will take before it started. So if you have 3
       machines and two quick to compile and one long to compile source file, you're not safe from a choice where everyone has to wait on the slow
       machine. Keep that in mind.

NETWORK SETUP FOR ICECREAM (FIREWALLS)
       A short overview of the ports icecream requires:

       o  TCP/10245 on the daemon computers (required)

       o  TCP/8765 for the the scheduler computer (required)

       o  TCP/8766 for the telnet interface to the scheduler (optional)

       o  UDP/8765 for broadcast to find the scheduler (optional)

       Note  that  the	SuSEfirewall2 on SUSE < 9.1 got some problems configuring broadcast. So you might need the -s option for the daemon in any
       case there. If the monitor can't find the scheduler, use USE_SCHEDULER=<host> icemon (or send me a patch :)

SEE ALSO

       icecream, scheduler, iceccd, icemon

ICECREAM AUTHORS

       Stephan Kulow <coolo@suse.de>

       Michael Matz <matz@suse.de>

       Cornelius Schumacher <cschum@suse.de>

       ...and various other contributors.

Icecream							 April 21th, 2005						       ICECREAM(7)