Recently, running cmake on my Macbook Pro under Mavericks had been taking extraordinarily long. To configure a moderately-sized project (~3000 source files, 159 CMakeLists.txt files) I had to wait 30 seconds! On the “CMake Performance Tips” page, they mention that configuring VTK, a very large project, took 14 seconds. Clearly something was wrong.

For me, the problem seemed to mostly manifest itself in the “generating” stage of CMake’s build process, which took more than half of that time. I tried profiling cmake with Instruments, but after about ten seconds, the cmake process stopped generating any CPU usage. That seemed strange, but indicated that perhaps it wasn’t cmake but some other process that was causing it to run so slowly.

I ran the excellent htop while configuring and found the culprit! opendirectoryd was consistently above 40% CPU usage during CMake’s generation stage. Some searches led me to a related superuser post which indicated that broken symlinks to /home could cause opendirectoryd to get busy. I searched my Dropbox for any similar problems, but didn’t find anything similar.

However, I do use Dropbox to sync my system configuration files (e.g. .gitconfig, .bashrc) across Mac and Linux systems. Scanning my .bashrc I found some old references to /home subdirectories in my $PATH. After tidying up my $PATH by removing the missing directory, I re-ran cmake and it only took 10 seconds. Apparently opendirectoryd burns a lot of cycles looking for missing directories in your $PATH, so I’m going to add checks throughout my .bashrc to ensure that a directory exists before adding it.

© Jack Morrison 2018

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