path: root/doc/man-icecream.7.docbook

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<refentry lang="&language;">
<refentryinfo>
	<title>Icecream User's Manual</title>
	<author>
          <personname>
            <firstname>Cornelius</firstname>
            <surname>Schumacher</surname>
          </personname>
        </author>
	<date>April 21th, 2005</date>
	<productname>Icecream</productname>
</refentryinfo>

<refmeta>
	<refentrytitle>Icecream</refentrytitle>
	<manvolnum>7</manvolnum>
</refmeta>

<refnamediv>
	<refname>Icecream</refname>
	<refpurpose>A distributed compile system</refpurpose>
</refnamediv>

<refsect1>
<title>Description</title>

<para>Icecream is a distributed compile system for C and C++.</para>

<para>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 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.</para>

</refsect1>
 
<refsect1>
<title>How to use icecream</title>

<para>You need:</para>
<itemizedlist>
<listitem>
  <para>One machine that runs the scheduler ("./scheduler -d")</para>
</listitem>
<listitem>
  <para>Many machines that run the daemon ("./iceccd -d")</para>
</listitem>
</itemizedlist>

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

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

<para>If you want funny stats, you might want to run "icemon".</para>
</refsect1>

<refsect1>
<title>Using icecream in heterogeneous environments</title> 

<para>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 <command>icecc --build-native</command> 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
<command>ICECC_VERSION=&lt;filename_of_archive_containing_your_environment&gt;</command>
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.
</para>

<para>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 :)</para>
</refsect1>

<refsect1>
<title>Cross-Compiling using icecream</title> 

<para>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 &lt;native_filename&gt;(,&lt;platform&gt;:&lt;cross_compiler_filename&gt;)*,
for example like this:
<literal>/work/9.1-i386.tar.bz2,ia64:/work/9.1-cross-ia64.tar.bz2</literal>
</para>

<para>How to package such a cross compiler is pretty straightforward if you look
what's inside the tarballs generated by <command>icecc --build-native</command>.</para>
 
</refsect1>

<refsect1>
<title>Cross-Compiling for embedded targets using icecream</title>

<para>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.</para>
 
<para>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 <varname>$ICECC_CC</varname>
and <varname>$ICECC_CXX</varname> you need to tell icecream which compilers to
use for preprocessing and local compiling. e.g. set it to
<command>ICECC_CC=arm-linux-gcc</command> and
<command>ICECC_CXX=arm-linux-g++</command>.</para>
 
<para>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.</para>
 
<para>Finally one needs to set <varname>ICECC_VERSION</varname> and point it to
the tar.bz2 you've created. When you start compiling your toolchain will be
used.</para>
 
<para>NOTE: with <varname>ICECC_VERSION</varname> you point out on which
platforms your toolchain runs, you do not indicate for which target code will be
generated.</para>

</refsect1>

<refsect1>
<title>How to combine icecream with ccache</title>

<para>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

<screen> 
 cat /opt/ccache/bin/g++:
 
 #! /bin/sh
 
 export CCACHE_PATH=/opt/icecream/bin
 export PATH=/opt/icecream/bin:/usr/bin:$PATH
 ccache g++ "$@"
</screen>
</para>

<para>Then you can replace /opt/icecream/bin with /opt/ccache/bin in your
<varname>$PATH</varname> and all icecream calls will go through ccache (and Qt
will compile in 62s :)</para>
 
<para>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).</para>

</refsect1>

<refsect1>
<title>Debug output</title>

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

</refsect1>

<refsect1>
<title>Some Numbers</title>

<para>
Numbers of my test case (some STL C++ genetic algorithm)
<itemizedlist>
  <listitem>
    <para>g++ on my machine: 1.6s</para>
  </listitem>
  <listitem>
    <para>g++ on fast machine: 1.1s</para>
  </listitem>
  <listitem>
    <para>icecream using my machine as remote machine: 1.9s</para>
  </listitem>
  <listitem>
    <para>icecream using fast machine: 1.8s</para>
  </listitem>
</itemizedlist> 
</para>

<para>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.</para>
 
<para>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).</para>
 
<para>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.</para>
 
<para>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
<itemizedlist>
  <listitem>
    <para>g++ -j1 on my machine: 3.2s</para>
  </listitem>
  <listitem>
    <para>g++ -j1 on the fast machine: 2.2s</para>
  </listitem>
  <listitem>
    <para>using icecream -j2 on my machine: max(1.7,1.8)=1.8s</para>
  </listitem>
  <listitem>
    <para>(using icecream -j2 on the other machine: max(1.1,1.8)=1.8s)</para>
  </listitem>
</itemizedlist> 
</para>

<para>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.</para>

</refsect1> 

<refsect1>
<title>What is the best environment for icecream</title>

<para>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.</para>
 
<para>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.</para>
 
<para>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.</para>
 
</refsect1>

<refsect1>
<title>Network setup for Icecream (firewalls)</title>

<para>A short overview of the ports icecream requires: 
 <itemizedlist>
  <listitem>
    <para> TCP/10245 on the daemon computers (required) </para>
  </listitem>
  <listitem>
    <para> TCP/8765 for the the scheduler computer (required) </para>
  </listitem>
  <listitem>
    <para> TCP/8766 for the telnet interface to the scheduler (optional) </para>
  </listitem>
  <listitem>
    <para> UDP/8765 for broadcast to find the scheduler (optional) </para>
  </listitem>
</itemizedlist>
</para>

<para>Note that the SuSEfirewall2 on SUSE &lt; 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=&lt;host&gt; icemon (or send me a patch :)</para>
 
</refsect1>


<refsect1>
<title>See Also</title>
<para>icecream, scheduler, iceccd, icemon</para>
</refsect1>

<refsect1>
<title>Icecream Authors</title>
<para>Stephan Kulow &lt;coolo@suse.de&gt;</para>
<para>Michael Matz &lt;matz@suse.de&gt;</para>
<para>Cornelius Schumacher &lt;cschum@suse.de&gt;</para>
<para>...and various other contributors.</para>
</refsect1>
</refentry>