Try speeding up CI builds

[claremacrae]

Feedback is painfully slow from our Travis and AppVeyor CI builds now:

• Travis: 40 - 45 minutes elapsed time
  • 13 configurations - each taking 3 to 4 minutes
• AppVeyor - 18 minutes
  • Cygwin: 11 minutes
  • Mingw 7.5 minutes
  • Some of the pain here is the queue time, which is probably outside our control

[claremacrae]

Travis CI build times.xlsx

This shows that even on Linux, where Boost needs to be downloaded - which takes around 20-25 seconds, the bulk of the elapsed time is on the compile and link stage - suggesting that it's worth trying ccache.

[claremacrae]

Travis: 40 - 45 minutes elapsed time

I misread that - it's saying:

• "Ran for 12 min 12 sec"
• "Total time 43 min"

So we aren't having to wait for 43 mins - but even so, it would be nice to have feedback sooner - before we have moved on to other things...

[claremacrae]

Following the Travis instructions for enabling ccache (https://docs.travis-ci.com/user/caching/#ccache-cache):

Effect on Build Timings

Step	Total build time	Build log
Before enabling ccache	43 min 33 sec	#83
First build after enabling ccache	60 min 55 sec	#84
Second build after enabling ccache (no code changes)	39 min 33 sec	#85

Consequences of ccache - first implementation:

OS	Compiler	Effect
Ubuntu	gcc	Better! ccache adds about 10 seconds to build time - but then takes at least 2 minutes off a repeat build - so really well worth it.
Ubuntu	clang	Worse! ccache adds a few seconds to build time - and then build time is even worse on repeat build - adding about 30 seconds per build
macOS	Xcode	Massively worse! ccache increases build macOS times from 3-4 minutes to 5-10 minutes for the initial build - and then 2 mins 20 to 8 mins 40 for repeat build

[claremacrae]

Useful links to improve the macOS builds - and maybe clang too:

• http://www.brianlheim.com/2017/08/20/supercollider-travisci.html
• https://crascit.com/2016/04/09/using-ccache-with-cmake/
• https://pspdfkit.com/blog/2015/ccache-for-fun-and-profit/
• https://github.com/travis-ci/travis-ci/issues/6201

[claremacrae]

Tool to validate Travis config: https://config.travis-ci.com/explore

[claremacrae]

This may help: https://github.com/argakiig/nano_imgui/blob/7ed76e27fb50732c0b3747c81784b8e4d83dc521/.travis.yml

[claremacrae]

By https://github.com/claremacrae/ApprovalTests.cpp/commit/0b826b252ab00fa4eb923ba737465c6d85f13e34 I have got the total build time down to 22 min 31 sec!

Most repeat builds take between

• 1 min 20 secs to
• 1 min 50 secs

The outlier is Xcode 8.1.0 on a max)S 10.12 (Sierra) image, which taks 4 min 10 secs'.

Since Apple dropped support for that OS in October 2019, I don't plan to spend any time on improving build times on that configuration, so I'll remove it from the Travis build matrix instead.

[claremacrae]

Current status of Travis builds on the travis_ccache branch of my fork:

Step	Elapsed built time	Total build time	Build log
Before enabling ccache	12 min 12 sec	43 min 33 sec	#83
First build after enabling ccache	16 min 16 sec	60 min 55 sec	#84
Second build after enabling ccache (no code changes)	11 min 09 sec	39 min 33 sec	#85
Second build after using Craig Scott mechanism to properly enable ccache in Makefiles, Ninja and XCode	12 min 05 sec	42 min 49 sec	#89
Second build after also stopping home-brew from updating all packages	7 min 06 sec	22 min 31 sec	#90
Second build after dropping support for Xcode 8.3 (macOS 11.12 Sierra)	6 min 08 sec	17 min 01 sec	#91
Repeat of the above (so some variability)	6 min 16 sec	18 min 37 sec	#93

[claremacrae]

I think the only potential big gain now would be to cache the Boost download between Linux builds - which I would have to do manually, so which would complicate the script somewhat.

There are some hints on how to do that in this change: https://github.com/loot/loot/commit/863939c2c51b6f5a14f264cf71b7809f58b34c8a

[claremacrae]

Commits for this are on a branch on my fork: https://github.com/claremacrae/ApprovalTests.cpp/commits/travis_ccache

[claremacrae]

There are some useful links in this: https://github.com/marketplace/actions/conan-cache

[claremacrae]

Possibly also useful: https://raymii.org/s/articles/Github_Actions_cpp_boost_cmake_speedup.html

[claremacrae]

We deleted Travis builds in e54031bef345a6fb2d696e5a0fff9020d826a699 - and can live with the AppVeyor times for now, so I'm closing this issue.