icecream(7)icecream(7)NAMEicecream - 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 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.
HOW TO USE ICECREAM
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/pro‐
file 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 com‐
piler 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_contain‐
ing_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 pro‐
vided 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 :)
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_VER‐
SION 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 symlinks
are in the path and before the path of your toolchain, with $ICECC_CC
and $ICECC_CXX you need to tell icecream which compilers to use for
preprocessing and local compiling. e.g. set it to ICECC_CC=arm-linux-
gcc and ICECC_CXX=arm-linux-g++.
As the next step you need to create a .tar.bz2 of your cross compiler,
check the result of build-native to see what needs to be present.
Finally one needs to set ICECC_VERSION and point it to the tar.bz2
you've created. When you start compiling your toolchain will be used.
NOTE: with ICECC_VERSION you point out on which platforms your
toolchain runs, you do not indicate for which target code will be gen‐
erated.
HOW TO COMBINE ICECREAM WITH CCACHE
The easiest way to use ccache with icecream is to set CCACHE_PREFIX to
icecc (the actual icecream client wrapper)
export CCACHE_PREFIX=icecc
.fi
This will make ccache prefix any compilation command it needs to do with icecc,
making it use icecream for the compilation (but not for preprocessing alone).
To actually use ccache, the mechanism is the same like with using icecream alone.
Since ccache does not provide any symlinks in /opt/ccache/bin, you can create them manually:
mkdir /opt/ccache/bin
ln -s /usr/bin/ccache /opt/ccache/bin/gcc
ln -s /usr/bin/ccache /opt/ccache/bin/g++
.fi
And then compile with
export PATH=/opt/ccache/bin:$PATH
.fi
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).
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).
AVOIDING OLD HOSTS
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 automati‐
cally 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
export ICECC_IGNORE_UNVERIFIED=1
.fi
SOME NUMBERS
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 com‐
piler can't interleave preprocessing with compilation and the file
needs to be read/written once more and in between the file is trans‐
fered.
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 com‐
puter 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.
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 paral‐
lelization, 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:
· 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_SCHED‐
ULER=<host> icemon (or send me a patch :)
SEE ALSO
icecream, icecc-scheduler, iceccd, icemon
ICECREAM AUTHORS
Stephan Kulow <coolo@suse.de>
Michael Matz <matz@suse.de>
Cornelius Schumacher <cschum@suse.de>
...and various other contributors.
April 21th, 2005 icecream(7)
