Jemalloc Rails

gistfile1.txt

We tried this about a year or so ago.  We didn't see any memory or performance savings at the time, but I'm not sure about our methodology...  

Eveything I've read about this indicates decent to great memory/peformance gains:  

(Nate Berkopec is big in the Rails perfomance game, and recommends everyone use it.)
https://www.speedshop.co/2017/12/04/malloc-doubles-ruby-memory.html

Other good writeups:
http://engineering.appfolio.com/appfolio-engineering/2018/2/1/benchmarking-rubys-heap-malloc-tcmalloc-jemalloc
https://www.mikeperham.com/2018/04/25/taming-rails-memory-bloat/
https://medium.com/@adrienjarthon/ruby-jemalloc-results-for-updown-io-d3fb2d32f67f
https://brandonhilkert.com/blog/reducing-sidekiq-memory-usage-with-jemalloc/

Installation:
We were trying a much harder installation at the time... Compiling ruby with jemalloc.  We should be able to simply:

sudo apt-get install libjemalloc-dev

LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libjemalloc.so.1 rails s puma

If you run with MALLOC_CONF=stats_print:true you get lots of fun stats after ending the process, which also confirms your ruby is using jemalloc.

LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libjemalloc.so.1 MALLOC_CONF=stats_print:true irb

For our legacy environments, or to install with jemalloc compilied into ruby:

- rvm install 2.4.0-jem -C --with-jemalloc  (I named mine 2.4.0-jem, but it can just be ruby version)

- This command should show -ljemalloc after
  ruby -r rbconfig -e "puts RbConfig::CONFIG['LIBS']"
  -lpthread -ljemalloc -lgmp -ldl -lcrypt -lm

- This command will also verify
  MALLOC_CONF=stats_print:true irb
  on irb `exit`
  we should see `___ Begin jemalloc statistics ___`


Jemalloc details:
https://www.facebook.com/notes/facebook-engineering/scalable-memory-allocation-using-jemalloc/480222803919/