On Fri, Jul 22, 2016 at 5:29 AM, Paolo Amadini <paolo.02....@amadzone.org> wrote:
> I build mozilla-central on OS X 10.9.5 with the latest compatible > version of XCode. > > $ clang --version > Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn) > Target: x86_64-apple-darwin13.4.0 > Thread model: posix > > A clobber build with a plain .mozconfig file takes about 15 minutes. > > As a result of bug 1286204 (require at least clang 3.6) the build broke, > and I had to install a newer version of clang: > > $ brew install llvm --with-clang > > $ /usr/local/opt/llvm/bin/clang --version > clang version 3.8.1 (tags/RELEASE_381/final) > Target: x86_64-apple-darwin13.4.0 > Thread model: posix > InstalledDir: /usr/local/opt/llvm/bin > > I've added these lines to .mozconfig: > > CC=/usr/local/opt/llvm/bin/clang > CXX=/usr/local/opt/llvm/bin/clang++ > > The same revision takes about 26 minutes to build. > > I've tested on changeset feaaf1af1065, which is obviously from before > the new requirement was introduced, with the .mozconfig being the only > difference between the two builds. > > Any suggestions on how to avoid this build time regression? > That's an intriguing result. Unfortunately, I can't reproduce because my MacBook Pro has CPU overheating problems so I can't get reliable build times from it. Does ccache come into play at all? If you run `time ./mach build`, does the user/sys CPU time have a drastic increase as well? Are the numbers the same across invocations? (Perhaps your machine overheats, like mine, and slows down after a few minutes of building.)
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