It appears that the new bundler 1.4.0 will support parallel gem installation. Thanks to thoughtbot's post that brought that to my attention :)

Now, since I've been dealing daily with GitLab for the past four months, I thought it would be a good candidate for testing.

I tried it on my production server which is a QEMU VM machine. Here are the specs¹:

Operating System  : Debian 7
Linux kernel      : 3.2.0-4-amd64
RAM               : 4GB
CPU               : 4-cores

On to the installation of bundler's pre version:

gem install bundler --pre

Next step the actual benchmarking. Make sure you either perform a new GitLab installation or remove the vendor/bundle/ directory. I used the same command the official installation suggests:

RAILS_ENV=production bundle install --without postgres development test aws

and I kept track of the output of four different numbers of jobs to run in parallel. As you'll see, the recommended option is to use as many jobs as your cpu cores.

Next table depicts the difference in gem installation time which is pretty impressive.