by gaffneyc

GitHub Readme.md


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/gaffneyc/heroku-buildpack-jemalloc.git
git push heroku master

Made possible by Dead Man's Snitch

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

Per dyno

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


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

Available Versions

Version Released 3.6.0 2015-04-15 4.0.4 2015-10-24 4.1.1 2016-05-03 4.2.1 2016-06-08 4.3.1 2016-11-07 4.4.0 2016-12-04 4.5.0 2017-02-28 5.0.1 2017-07-01 5.1.0 2018-05-08 5.2.0 2019-04-02 5.2.1 2019-08-05 5.3.0 2022-05-06

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


This uses Docker to build against Heroku stack-image-like images.

make VERSION=5.1.0

Artifacts will be dropped in dist/ based on Heroku stack and jemalloc version.

Deploying New Versions

  • make VERSION=X.Y.Z
  • open dist
  • Go to releases
  • Edit the release corresponding to each heroku Stack
  • Drag and drop the new build to attach

Creating a New Stack

  • Go to releases
  • Click "Draft a new release"
  • Tag is the name of the Stack (e.g. heroku-18)
  • Target is release-master
  • Title is Builds for the [stack] stack