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Reduce C/C++ Compile Time With distcc
An anonymous reader writes "Some people prefer the convenience of pre-compiled binaries in the form of RPMs or other such installer methods. But this can be a false economy, especially with programs that are used frequently: precompiled binaries will never run as quickly as those compiled with the right optimizations for your own machine. If you use a distributed compiler, you get the best of both worlds: fast compile and faster apps. This article shows you the benifits of using distcc, a distributed C compiler based on gcc, that gives you significant productivity gains."
While distCC is a great tool, there are a couple things to mention. First, the article blurb states that distCC is "a distributed compiler based on GCC." It is actually a method of passing files to GCC on a remote computer in such a way that the build scripts think it was done locally.
The article also says that other than distCC, the computers need not have anything in common; this is not strictly true. Different major versions of GCC can cause problems if you are trying to compile with optimization flags that are only on the newer version. I have run into this on my gentoo box, trying to use an outdated version of GCC on a redhat box.
Another thing is that some very large packages have trouble with distributed building of any sort (either multiple threads on the same machine, or over a network like with distCC). As far as I know, at least parts of xfree86, KDE and the kernel turn off distributed compiling during the build. Some of this might just be in the gentoo ebuilds, but I tink some of it is in the actual Makefiles. If a program has trouble compiling, it's always worth a shot to turn off distCC.
A good resource for setting up distCC on a gentoo system (since compiling is so large of gentoo, this is particularly important) is gentoo.org's own distCC guide
It's also been been discussed here on Slashdot (two years ago!) in "A Distributed Front-end for GCC" and earlier this year in "Optimizing distcc."
Distcc is great for installing Gentoo on an older computer because you can have other (faster) computers help with the compile, and if you like distcc, you may also like ccache.
That's why I use Gentoo!
I think nc can be used like distcc by redefining CC="nc gcc". However, more commonly it is done by putting $(NC) at the beginning of the build rules. Then you can use nc for any build rules, not just C compiles.
In addition to use with make, nc works well with SCons.
Compare the speed cost of loading a "generic" binary to an "optimised" one, multiply by the number of times you load that binary.
Then look at the time required to compile the optimised copy.
How often, in the lifetime of a particular version of a binary, do you really need to reload it?
The promise of distcc is closely related to source distributions like Gentoo. The benefit is overstated. Don't waste your time.
Quick wafting zephyrs vex bold Jim
We use the distcc that Apple distributes with XCode even though we dont' use XCode itself. It really helps to get a few dual-CPU G5's working!
The cool thing about Apple's version is that by default it uses Rendezvous to determine which machines are available to distribute work to.
There are still enterprise uses where coders need to compile huge projects from scratch that take too long on a single workstation. Instead of that build taking 15 minutes on a single workstation, they can tap the power of all the workstations and build it in a few minutes or perhaps even seconds.
thisnukes4u.net
It's news to people that don't read slashdot every day.
I don't mind revisiting older topics once in awhile - it's only annoying when it's two days in a row. And even then, it's not that big of a deal, I simply pass over it.
Posts like this are more waste of space then then a duplicate article post, and you get a lot more posts like yours then we do dupes. It's especially annoying when people say "We talked about this TWO YEARS AGO!!!" Well here's some news for you: I don't memorize every slashdot story since the beginning, and there's been a lot of new members since then.
- It's not the Macs I hate. It's Digg users. -
I've spent the last week setting up a Gentoo cluster with distcc and I've noticed a few things:
1. when *recompiling*, the advantage due to ccache far outweighs the performance of distcc on the first compile. If you're testing distcc you need to be aware of this and disable ccache.
2. most large packages either disable distcc (e.g. xfree by limiting make -jX) or compile small sets of files in bursts and spend the majority of time performing non-compilation and linking. Distcc helps with the compilation but because it's only a small part of the total build time, the overall improvement isn't as great as you might have hoped.
3. distccmon-gnome is very cool.
4. using distcc with Gentoo transparently involves modifying your path and this can make non-root compilations troublesome (permissions on distcc lock files). I haven't figured this one out yet other than to specify the full path to the compiler: make CC=/usr/bin/gcc rather than CC=gcc.
5. the returns from adding an extra distcc server to the pool drop considerably after the first few machines. Even on a 1 gigabit LAN the costs of distcc catch up with the benefits after a while. This is more of a concern when compiling lots of small files.
6. it can handle cross-compilation with a bit of configuration.
So although distcc can often reduce build time, it's not quite as effective as you might assume or hope at first.
precompiled binaries will never run as quickly as those compiled with the right optimizations for your own machine
A straw man. Precompiled binaries may have been compiled with the optimal settings for your machine, and binaries which you compile may not have the optimal settings. Identifying the optimal settings can actually be non-trivial. Source-based distributions are not necessarily the best fix to the 'one-size-fits-all' approach used by some distro's.
I came across distcc by chance about 4 months ago, and I must say, it has utterly improved things around here.
:-( ).
We reguarly develop/compile/debug a moderate-small sized software package, typically taking about 1 minute per compile. Now, while 1 minute doesn't sound like a long time, it starts adding up when you find yourself recompiling 100+ times a day.
With the inclusion of distcc into the whole situation, we're able to reduce that 1 minute compile down to a little less than 20 seconds; highly appreciated (although now we have less excuses to go get a coffee
Distcc is a great package which can be extremely useful.
PLD.
The obvious and most popular answer is encoding video. I think a great many people do a lot of this. Since no processor is fast enough to encode DVD-res video at 16X, it isn't bound by IO speeds either. I can start videos encoding in far less time than it takes to complete the process as well. Pure CPU number-crunching.
Other applications are any form of crypto. Reduce the time you have to wait for PGP to encrypt. Reduce the delay on your SSH sessions.
Then there are databases. Sure, they're often IO bound, but it is commonly a CPU limitation.
Also any heavy-load service. If apache is serving lots of threads, especially PHP/Perl compiled pages, you are going to be maxing out your CPU.
Then there are the programs that are just bloated. Mozilla/Firefox is still quite slow, and I can open pages far, far faster than they can be rendered. Anything that makes it even 1% faster is very welcome, as those savings eventually add-up to large ammounts of time.
If you really never use any of those, hooray for you, but most people certainly do.
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
But this can be a false economy...
Every time something that is distributed in binary is rebuilt from source for local use, by definition it's to change some assumption that was inherent in the testing of the original binary (or else the binary distribution would suffice). And with that, some non-0 confidence that was built into the binary release by that testing is wiped out and must be recovered by local analysis and testing (i.e., time and effort) or reduced expectations. Otherwise, it's running on blind faith. This is particularly true with programs that are used frequently, i.e., one expects to depend on them repeatedly. So in my mind, "the best of both worlds" is more meaningful if it refers to fast and reliable apps. I don't care how fast the compiler is if I can't trust the results anymore. That is a different economy equation, and completely justifes the "convenience" of pre-compiled binaries in many applications.
At the moment there's a bug in Linux kernel 2.4.26 that causes the remote compiling systems to encounter a kernel panic (and crash.)
It's a known bug and has been discussed on the lkml. The bug is also discussed on the gentoo bugzilla. A patch is also available, though the patch program didn't work for me so I had to apply it manually.
The patch seems to be holding up, too. If you're using distcc on systems with vanilla 2.4.26 kernels, I'd suggest patching them.
-kidlinux.
For those using Visual Studio on Windows, I highly recommend a tool called Incredibuild to do the same job. It is not free like distcc, but is very effective and integrates nicely with Visual Studio. It cut my build time for a project at work from 15 minutes to 1 minute 20 seconds. Nice!
kingos
... was just released.
Only available on mirrors, currently.
Belief is the currency of delusion.
Absolutely, I use it at home all the time. It's great for sofa computing: sit on the sofa with a modest laptop, and send your compile jobs across a wireless network to a faster machine in the study.
If you use the LZO compression option then it's quite useful even on 5Mbps wireless.
You can also tell distcc to run as many jobs remotely as possible to keep the laptop from scorching your lap.
It's really nice to be able to build the kernel from source in a reasonable time on a 800MHz machine.