What is ARR_WORDS in a GHC heap profile?

Question

The heap profile for my program, generated by ./program +RTS -hy -p, is dominated by "ARR_WORDS". It doesn't correspond to anything obvious in my program; is it a GHC internal of some sort? How should I treat its dominating appearance in the profile?

I'm using GHC 7.0.3.

Answer 1

ARR_WORDS is the internal name of ByteArray#, which is a GHC type used to implement e.g. ByteString, Text and unboxed arrays.