http://bugs.winehq.org/show_bug.cgi?id=30148
--- Comment #19 from julusp@gmail.com 2012-04-07 22:12:22 CDT --- (In reply to comment #18)
mmap is very slow on Mac OS, there's nothing we can do about that.
I made some test myself (mmap/munmap) and the MAP_PRIVATE flag makes really slow: MAP_PRIVATE 1000 mmaps (real/user/sys): 20.717s/0.008s/20.671s MAP_SHARED 1000 mmaps (real/user/sys): 0.010s/0.001s/0.008s
same script on linux MAP_PRIVATE 1000 mmaps (real/user/sys): 0.008s/0.000s/0.008s
according to vmmap command, game uses MAP_PRIVATE.
also I found old communication about git, describing the same problem on osx. Linus suggested to use pread() instead, and the result was: from (estimated) 37 minutes using mmaps to 52 seconds using pread(). source: http://www.spinics.net/lists/git/msg18258.html