Ruby Memory Issues and Where to Find Them 
Memory Bloat
When code tries to allocate a lot of objects simultaneously.
Where to find: process big json or XML file in none streaming manner, or load a big number of objects from the database without batching.
Symptoms: "stepwise jumps" in memory.
Ruby Leak
When reference to object lives longer than expected.
Where to find: caching, memoization, i18n.
Examples:
- http://blog.skylight.io/hunting-for-leaks-in-ruby/
- https://github.com/discourse/discourse/commit/830ce05fe64fd310d26d7da87ea6e4076696b7c8
Symptoms: constant grows in memory.
Image credit: samsaffron.
C Leak
When the leak happens in C-land.
Examples:
Object Grinder
This is not commonly recognized as a memory issue, but it is one. Happens when code uses a lot of temporary objects, which leads to increased pressure on GC and to memory fragmentation.
Where to find: everywhere.
Examples:
- default arguments fastruby/fast-ruby#137
- string literals without freeze (
# frozen_string_literal: true)
Symptoms: logarithm-like memory growth.
Memory Hog
Not commonly recognized as a memory issue, but it is one. Happens when code loads big sets of data and never unloads them.
Where to find: data gems.
Examples: