More build statistics and data
The next idea to try in our journey to get fast builds was to try
building everything in memory. For this purpose, we will compare the
data with our previous results. The fastest build done on disk with 13
parallel directories built at the same time was 1 hour 38 minute
without ccache or 33 minutes with ccache (ccache saving was
approx. 66% when building on disk).
The same builds done in memory (on tmpfs) were 1 hour and 35 minutes
(without ccache) or 29 minutes (with ccache). This time, ccache was on
the disk, so I tried with ccache cache in memory but the result was
the same (I'm building on machine with 16GB or RAM, enough for buffer
To sum up if you are about to build a new build machine for Linux: it
is better to have more (even slower) processors/cores than having the
most powerful processors available! Instead of throwing your money out
of the window, spend your time on optimizing your build parameters for
your environment (and you can also help us with fixing parallel build
issues ;-). This means that for our new build server, I'll target the
slowest possible quad Xeon (5310), one single processor in a dual
The tmpfs gain is not that significant if you have enough
RAM so it is not worth the effort. And to be able to build in RAM, you
must have enough RAM anyway ;-)
If you have other ideas what to measure/compare on this machine, just
ping me on IRC or via mail.
In the next blog entry, I'll analyze the overall build data a bit.