Ruby 2.1.1 introduces a new environment variable, RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR, that helps to mitigate the heap growth caused by the generational garbage collector added in 2.1. By setting this variable to a value lower than the default of 2 (we are using the suggested value of 1.3) you can indirectly force the garbage collector to perform more major GCs, which reduces heap growth.
See https://bugs.ruby-lang.org/issues/9607 for more information.