On Tue, 16 Jul 2019 at 18:29, Christian Gagneraud <[email protected]> wrote: > > Hi there, > > I finally found time to start my qbs vs cmake build perf. > > What i found is that qbs beats cmake 'big time' on my build machine > and i was actually surprised, so surprised that i'm trying to find > where is the mistake.
Here is a graph showing qtcreator build time vs number of parallel jobs, using cmake and qbs. Builds were done in a docker container (same for both), stock Ubuntu 19.04/amd64, all dependencies (inc. qbs tool and dev libs) installed using apt. Number of compilations were measured by generating a Clang compilation database and counting the number of entries: cmake: 2881 (2869) qbs: 4362 (2848) The first number is the number of compiler calls, the second number if the same but ignoring the pattern 'moc_'. Using 2 jobs: qbs: 26:30.78 cmake: 30:11.44 =>Cmake is 15% slower than qbs Using 56 jobs: qbs: 2:35.95 cmake: 4:33.79 => CMake is 75% slower than bqs At the 20 jobs mark, cmake start to stagnate, whereas qbs still make use of parallelism, at the 30 jobs mark, cmake completely stopped reducing overall build time, whereas qbs start to stagnate. At the 40 jobs mark, both systems are stale. Chris
qtcreator-build-time-cmake-vs-qbs.pdf
Description: Adobe PDF document
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