ghc-trace-events provides faster traceEvent and traceMarker as well as
arbitrary binary object logging for the eventlog framework. Unlike the
eventlog tracing functions in base, all the tracing functions in this
library don't evaluate the input if user event logging (the -lu flag) is
disabled, which can give a significant boost in performance.

Homepage:
http://hackage.haskell.org/package/ghc-trace-events
