heroku-buildpack-jemalloc

jemalloc is a general purpose malloc implementation that works to avoid memory fragmentation in multithreaded applications. This buildpack makes it easy to install and use jemalloc on Heroku and compatible platforms.

heroku buildpacks:add --index 1 https://github.com/retailzipline/heroku-buildpack-jemalloc.git
git push heroku master

Continued development and support of the jemalloc buildpack is sponsored by Dead Man's Snitch.

Ever been surprised that a critical recurring job was silently failing to run? Whether it's backups, cache clearing, sending invoices, or whatever your application depends on, Dead Man's Snitch makes it easy to monitor heroku scheduler tasks or to add cron job monitoring to your other services.

Get started for free today with Dead Man's Snitch on Heroku

Set the JEMALLOC_ENABLED config option to true and jemalloc will be used for all commands run inside of your dynos.

heroku config:set JEMALLOC_ENABLED=true

To control when jemalloc is configured on a per dyno basis use jemalloc.sh <cmd> and ensure that JEMALLOC_ENABLED is unset.

Example Procfile:

web: jemalloc.sh bundle exec puma -C config/puma.rb

Set this to true to automatically enable jemalloc.

heroku config:set JEMALLOC_ENABLED=true

To disable jemalloc set the option to false. This will cause the application to restart disabling jemalloc.

heroku config:set JEMALLOC_ENABLED=false

While jemalloc's default configuration works well in most situations it does provide a set of options to fine tune performance and memory usage. You can find a full list of options in the jemalloc documentation.

Many Rails applications benefit from a common set of options and the below was added as the default with dockerfile-rails as of Rails 7.1. While this is a good default for most Rails apps it prefers performance over minimal memory usage. For more details on each option and other tested configs with different trade offs there is more info in this gist.

heroku config:set MALLOC_CONF=dirty_decay_ms:1000,narenas:2,background_thread:true

Set this to select or pin to a specific version of jemalloc. The default is to use the latest stable version if this is not set. You will receive an error mentioning tar if the version does not exist.

Default: 5.3.0

note: This setting is only used during slug compilation. Changing it will require a code change to be deployed in order to take affect.

heroku config:set JEMALLOC_VERSION=3.6.0

The complete and most up to date list of supported versions and stacks is available on the releases page.

Run make console to start up a shell in a test build environment that mimic's Heroku's build phase.