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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 distributes it to remote machines allowing a paral-
       lel 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 $prefix/bin is the first first	entry  in
       your  path,  e.g. type export PATH=/opt/icecream/bin:$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 homoge-
       neous 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=<file-
       name_of_archive_containing_your_environment>  in the shell environment where you start the
       compile 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 dif-
       ferent versions 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>(,<plat-
       form>:<cross_compiler_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 symlinks 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 compile 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
       disabled 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  compilations  (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 net-
       work, 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  com-
       pile  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 submitting machine (the one you called g++ on)
       will be fast enough to feed the others. Especially if your project consists of  many  easy
       to  compile  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)
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