MallocTrim

There is currently a proposal for the ruby language to call malloc_trim(0) on GC runs to more efficiently give memory back to the operating system. This is a gem giving access to malloc_trim to ruby land to ease testing.

require 'malloc_trim'
MallocTrim.trim # most effective when doing a GC.start before

For an explanation on why this works, read:

• https://www.joyfulbikeshedding.com/blog/2019-03-14-what-causes-ruby-memory-bloat.html

And find the official proposal for introducing this into ruby here:

• https://bugs.ruby-lang.org/issues/15667

Since malloc_trim is not available on MacOS systems, this won't have any effect there. Call MallocTrim.trimming_possible? to check whether malloc_trim is available.

For testing purposes, this gem also provides MallocTrim.enable_trimming (and it's counterpart disable_trimming) which calls malloc_trim after every GC run.

I, personally, found it most effective when running

GC.start
MallocTrim.trim

after a heavy job. This frees memory where repeated calls to only GC.start does not free any memory.

Add this line to your application's Gemfile:

gem 'malloc_trim'

And then execute:

$ bundle

Or install it yourself as:

$ gem install malloc_trim

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment. Note that MacOS systems don't ship with malloc_trim so this gem will have nothing to do on these systems.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/tessi/malloc_trim. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the MallocTrim project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.