Significantly (23 to 33%) faster builds of qgis_core/analysis/3d/gui/app/server

[rouault]

by precompiling qgis.h

Needs to be precompiled for each target due to different includes, defines, etc. (~ 4 second for each target to build the precompiled header in below timings)

Executive summary:

• ~ 33% faster builds on ubuntu 22.04, QT5
• ~ 23% faster builds (only measured on qgis_core) on fedora:rawhide, QT6
• build artifact increase size: + ~7%
• shared library increase size: + 1% at most

Setup: laptop with Intel(R) Core(TM) i7-10750H CPU @ 2.60GHz, host OS Ubuntu 20.04, QGIS built in Docker
ccache and ${build_dir}/src/{component} directories emptied before each build

Details:

• ubuntu 22.04, QT5, regular, CMAKE_BUILD_TYPE=Debug

$ time make -j12 qgis_core
real	9m8.566s
user	90m24.917s
sys	    9m51.179s

$ du -c src/core | tail -n 1
1994796	total

$ ll ./output/lib/libqgis_core.so.3.41.0
-rwxr-xr-x 1 root root 590223936 Nov 30 00:35 ./output/lib/libqgis_core.so.3.41.0*

$ time make -j12 qgis_gui
real	8m26.430s
user	80m28.457s
sys	    11m27.936s

$ du -c src/gui | tail -n 1
1538440	total

$ ll ./output/lib/libqgis_gui.so.3.41.0
-rwxr-xr-x 1 root root 454560448 Nov 30 00:47 ./output/lib/libqgis_gui.so.3.41.0*

$ time make -j12 qgis_app
real	4m55.189s
user	47m4.876s
sys	    6m54.868s

$ du -c src/app | tail -n 1
783256	total

$ ll ./output/lib/libqgis_app.so.3.41.0
-rwxr-xr-x 1 root root 232041152 Nov 30 01:25 ./output/lib/libqgis_app.so.3.41.0*

• ubuntu 22.04, QT5, qgis.h as precompiled header, CMAKE_BUILD_TYPE=Debug:

$ time make -j12 qgis_core
real	6m3.472s
user	59m3.835s
sys	    5m22.424s

$ du -c src/core | tail -n 1
2137448	total

$ ll ./output/lib/libqgis_core.so.3.41.0
-rwxr-xr-x 1 root root 598395456 Nov 30 00:56 ./output/lib/libqgis_core.so.3.41.0*

$ time make -j12 qgis_gui
real	5m45.719s
user	53m30.107s
sys	    6m11.246s

$ du -c src/gui | tail -n 1
1660444	total

$ ll ./output/lib/libqgis_gui.so.3.41.0
-rwxr-xr-x 1 root root 456432320 Nov 30 01:04 ./output/lib/libqgis_gui.so.3.41.0*

$ time make -j12 qgis_analysis
real	2m36.504s
user	26m25.310s
sys	    2m17.601s

$ du -c src/analysis/ | tail -n 1
920912	total

$ ll ./output/lib/libqgis_analysis.so.3.41.0
-rwxr-xr-x 1 root root 228178496 Nov 30 01:11 ./output/lib/libqgis_analysis.so.3.41.0*

$ time make -j12 qgis_3d
real	0m43.710s
user	6m9.148s
sys	    0m39.859s

$ du -c src/3d | tail -n 1
315212	total

$ ll ./output/lib/libqgis_3d.so.3.41.0
-rwxr-xr-x 1 root root 58472960 Nov 30 01:14 ./output/lib/libqgis_3d.so.3.41.0*

$ time make -j12 qgis_app
real	3m35.156s
user	34m17.371s
sys	    3m52.111s

$ du -c src/app | tail -n 1
905160	total

$ ll ./output/lib/libqgis_app.so.3.41.0
-rwxr-xr-x 1 root root 232577728 Nov 30 01:19 ./output/lib/libqgis_app.so.3.41.0*

• fedora:rawhide, QT6, regular, CMAKE_BUILD_TYPE=Debug:

$ time ninja qgis_core
real	13m47.521s
user	134m48.546s
sys	    10m2.176s

$ du -c src/core | tail -n 1
2862200	total

$ ll ./output/lib/libqgis_core.so.3.41.0
-rwxr-xr-x 1 root root 824605072 Nov 30 00:53 ./output/lib/libqgis_core.so.3.41.0

• fedora:rawhide, QT6, qgis.h as precompiled header, CMAKE_BUILD_TYPE=Debug:

$ time ninja qgis_core
real	10m35.657s
user	97m51.161s
sys	    7m59.564s

$ du -c src/core | tail -n 1
3028420	total

$ ll ./output/lib/libqgis_core.so.3.41.0
-rwxr-xr-x 1 root root 825732184 Nov 30 00:38 ./output/lib/libqgis_core.so.3.41.0

[github-actions]

🪟 Windows builds

Download Windows builds of this PR for testing.
Debug symbols for this build are available here.
(Built from commit d698e77)

🪟 Windows Qt6 builds

Download Windows Qt6 builds of this PR for testing.
(Built from commit d698e77)

[nyalldawson]

Is this worth doing for src/server too? Great work!!

[rouault]

Is this worth doing for src/server too? Great work!!

Done. Most certainly given the consistency of benefits on other components (I'd say there's a benefit for any target with more than 10 .cpp files)