Provided by: icecc_1.0.1-1_amd64 bug


       icecream - A distributed compile system


       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 build and distributes 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.


       You need:

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

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

       If you want to compile using icecream, make sure $prefix/lib/icecc/bin is the first  first
       entry  in  your  path,  e.g.  type export PATH=/usr/lib/icecc/bin:$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".


       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 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
       different versions of your beloved SUSE Linux :)


       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_compiler_filename>)*,    for   example   like   this:

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


       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

       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.


       The easiest way to use ccache with icecream is to set CCACHE_PREFIX to icecc  (the  actual
       icecream client wrapper)

        export CCACHE_PREFIX=icecc

       This will make ccache prefix any compilation command it needs to do with icecc,
       making it use icecream for the compilation (but not for preprocessing alone).

       To actually use ccache, the mechanism is the same like with using icecream alone.
       Since ccache does not provide any symlinks in /opt/ccache/bin, you can create them manually:

       mkdir /opt/ccache/bin
       ln -s /usr/bin/ccache /opt/ccache/bin/gcc
       ln -s /usr/bin/ccache /opt/ccache/bin/g++

       And then compile with

       export PATH=/opt/ccache/bin:$PATH

       Note however that ccache isn't really worth the trouble if you're not
       recompiling your project 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).


       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).


       It is possible that compilation on some hosts fails because they are  too  old  (typically
       the  kernel  on  the  remote  host  is too old for the glibc from the local host).  Recent
       icecream versions should automatically detect this and avoid such hosts  when  compilation
       would  fail.  If  some  hosts  are running old icecream versions and it is not possible to
       upgrade them for some reason, use



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

       • g++ on my machine: 1.6s

       • g++ on fast machine: 1.1s

       • icecream using my machine as remote machine: 1.9s

       • 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

       • g++ -j1 on my machine: 3.2s

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

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

       • (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.


       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 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

       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.


       A short overview of the ports icecream requires:

       • TCP/10245 on the daemon computers (required)

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

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

       • 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 :)


       icecream, icecc-scheduler, iceccd, icemon


       Stephan Kulow <>

       Michael Matz <>

       Cornelius Schumacher <>

       ...and various other contributors.

                                         April 21th, 2005                             icecream(7)