Improve collaborative build times with ccache

By Martin C. Brown
2004-11-08

Statistics

Now that everything is set up, it is time to see how much of a difference it makes. I've run a series of tests here building Perl. We need something meaty to compile, because ccache works best when it has cached the parsed header files. This is just the make phase, which occurs after we've run a standard configure (using configure.gnu), and it includes all the stages, even those not related to compiling code. These non-compiler operations won't affect the overall statistics.

As previously mentioned, the effects of ccache won't be felt on the first compilation. It's the recompilation, where you are reusing previous preprocessor passes, that will make a difference. The recompile times in Table 1 are based on simply doing a touch on each of the C source files in the main Perl source directory. I've included the times for building with plain gcc, ccache+gcc, and ccache+distcc+gcc in a four-node network with various values of concurrent distcc jobs.

Table 1. The recompile times

Environment                        Time

gcc (first run)                    8m02.273s 

gcc (recompile)                    3m30.051s 

ccache+gcc (first run)             8m54.714s 

ccache+gcc (recompile)             0m45.455s 

ccache+distcc+gcc -j4              4m14.546s 

ccache+distcc+gcc -j4 (recompile)  0m38.985s 

ccache+distcc+gcc -j8  3m13.020s 

ccache+distcc+gcc -j8 (recompile)  0m34.380s

Wow! Just using ccache alone saves almost 3 minutes (well, 2 minutes and 45 seconds) on the build time of Perl, all because ccache has kept pre-parsed versions of the header files and used them in place of continually re-running cpp on each source file. Incorporating distcc into the process gives results in an overall speed increase as well as slightly faster recompile times.

Tutorial Pages:
» How to squeeze more speed out of your compilations
» Using ccache
» Combining ccache and distcc
» Statistics
» Summary
» Resources

First published by IBM DeveloperWorks

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