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: /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.


   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


   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

   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 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.


   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)


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