We don't formally support running WLS on Mac OS X (other than the WLS dev zip file for development purposes) the libmuxer native implementation is not ported to Mac OS X, so WLS will default to using Java I/O.
<Nov 29, 2011 6:19:40 PM GMT+00:05> <Error> <Socket> <BEA-000438> <Unable to load performance pack. Using Java I/O instead. Please ensure that libmuxer library is in :'.:/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java'