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UPDATE [30 Apr 2013]: The new, updated and faster version of this blog post covering Ruby 1.9.3 patchelevel 392 and railsexpress patch set.

I knew that there are various Ruby patches available but I’ve never tried them as I didn’t want to waste time for something that I thought I don’t really need.

Then I found out that rvm comes bundled with patches ready to be applied, so I’m just a simple command line away from having a patched Ruby. Don’t know how I missed that before.

One particular patch that worth trying is falcon. It improves startup time of big Ruby applications. And the bigger your Gemfile is the bigger the improvement.

Try it right now for yourself. It will only take a couple of minutes.

First upgrade rvm to make sure you have the latest

rvm get head

Then the actual Ruby build

rvm install 1.9.3 --patch falcon -n falcon

Note that this command can fail with the following error: Patch 'falcon' not found. The reason is that falcon patch is not yet supported on the latest Ruby patch level, in which case you will need to specify older patch level to make it work.

Find out what patchlevels have falcon support

ls $rvm_path/patches/ruby/1.9.3/*/*falcon* | sort

So latest patch level with falcon support is 286 at the time of this writing.

Install specific patch level with falcon support

rvm install ruby-1.9.3-p286 --patch falcon -n falcon

Congratulations, you now have a patched Ruby installed.

Lets test how much improvement it is. The following is for one of my current projects with about 50 gems:

✗ rvm use default
Using /usr/local/rvm/gems/ruby-1.9.3-p194
✗ time bin/rails runner "puts :OK"
bin/rails runner "puts :OK"  6.47s user 0.60s system 99% cpu 7.106 total
✗ rvm use ruby-1.9.3-p286-falcon
Using /usr/local/rvm/gems/ruby-1.9.3-p286-falcon
✗ time bin/rails runner "puts :OK"
bin/rails runner "puts :OK"  2.79s user 0.52s system 98% cpu 3.354 total

Nice! Startup time decreased from 3.354 to 1.106 seconds. More then twice faster.

I’m going to use this Ruby by default now

rvm use ruby-1.9.3-p286-falcon --default

And while we are on the “lets improve rails startup times” subject, lets do one more change. Add the following to your shell startup file. i.e. ~/.bashrc or ~/.zshrc

export RUBY_HEAP_MIN_SLOTS=1000000
export RUBY_HEAP_FREE_MIN=500000
export RUBY_GC_MALLOC_LIMIT=100000000

This will tune Ruby GC settings to be better suited for running big apps (as it seems to be tuned for small Ruby scripts by default).

Lets see how much improvement that is

time bin/rails runner "puts :OK"
bin/rails runner "puts :OK"  2.27s user 0.58s system 98% cpu 2.890 total

Total improvement from 7.106 to 2.890 is almost 60%.

Now, stop fiddling with the environment and go back to creating something great! :)