Tuning your Ruby GC for fun and profit

January 31, 2015 · Miguel Parramón · blogger

By simply adding the following to my .zshrc:

export RUBY_HEAP_MIN_SLOTS=2000000

export RUBY_HEAP_SLOTS_INCREMENT=500000

export RUBY_HEAP_SLOTS_GROWTH_FACTOR=1

export RUBY_GC_MALLOC_LIMIT=70000000

export RUBY_FREE_MIN=100000

I’m getting a 10% increase running the test suite on a Rails app:

# Before:

rake 24.57s user 3.77s system 95% cpu 29.690 total

# After:

rake 21.41s user 4.22s system 95% cpu 26.897 total

Try it out and see it for yourself :)