Simon Marlow authored Aug 30, 2016 and Ben Gamari committed Aug 31, 2016

This is long overdue.

Perhaps 1MB is a little on the skinny size, but this is based on
* A lot of commodity dual-core desktop processors have 3MB L3 cache
* We're traditionally quite frugal with memory by default

Test Plan: validate

Reviewers: erikd, bgamari, hvr, austin, rwbarton, ezyang

Reviewed By: ezyang

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2496