Document workaround for slow JRuby installation on GCE

[BanzaiMan]

One should install HAVEGED.

[BanzaiMan]

One could also argue that this should be automatic on JRuby installation.

[perlun]

Thanks for that. I tried this now in one of our repos. But it still takes about 2 minutes to install JRuby with this fix, and the sudo-based infrastructure means that the build starts slower as well. 😒

I noted that this list (from the build output):

Pre-installed Ruby versions
jruby-9.1.2.0
ruby-1.9.3-p551
ruby-2.0.0-p648
ruby-2.1.9
ruby-2.2.5
ruby-2.3.1

...doesn't contain jruby-9.1.5.0. Maybe that would be the quick and easy fix, that you add jruby-9.1.5.0 to the list of preinstalled ruby versions? Then it should be instant to rvm use that version in the builds.

[perlun]

Any progress on this? JRuby 9.1.5 builds are still, regretfully, taking minutes longer than builds on other (supported) jrubies. 😢

[perlun]

Still nothing? This is really really frustrating, since it slows all our builds down with 2 minutes. JRuby 9.1.5.0 was released a long time ago, it's really sad that Travis don't seem to care about the JRuby community.

[perlun]

9.1.6.0 is out now, so 9.1.5.0 is no longer so interesting. But good support for 9.1.6.0 is really, really important. I filed a separate bug about it: travis-ci/travis-ci#6892