Global big object heap allocator lock causes contention

The lock allocate takes when allocating big objects hurts scalability of I/O bound application. Network.Socket.ByteString.recv is typically called with a buffer size of 4096, which causes a ByteString of that size to be allocated. The size of this ByteString causes it to be allocated from the big object space, which causes contention of the global lock that guards that space.

See http://www.yesodweb.com/blog/2014/02/new-warp for a real world example.