Not Very Good MRI Heap Analyzer (Fork Me)

Getting a heap dump of your Rails application just after boot:
$ echo "require 'objspace'; ObjectSpace.trace_object_allocations_start" > x.rb
$ RAILS_ENV=production ruby -I. -rx -e'require "config/environment"; GC.start; puts ObjectSpace.dump_all.path'
This will print a file name that contains JSON representing your heap. Upload that file.

Allocations per Generation
selected out of records | Reset All
Type Count
Classes by size
Allocations by Method
Gems by Allocation Size