[Mono-osx] Horrible performance on Mac, need advice.

LKeene lionel.keene at gmail.com
Mon Jul 20 16:29:10 EDT 2009

Hello again folks.

As the title says, I'm getting GAWD-AWFUL performance with my app when
running on mono + Mac OS X.  The exact same binary runs in fluid
real-time on Mono + Windows. Mac performance is literally dozens of times
slower. It (meaning my app) cannot be used on Mac like this. I've gone from
real-time to unusably slow.

Here's what I'm seeing: I have data files that consist of 32-bit float
values stored as plain old raw binary files.  The data is read from the
disk, processed via some mathematical operations, then rendered on screen.
I'm using 2 threads to read the data; the first thread reads a scanline of
data from the disk, copies it to a temp buffer, signals the other thread and
waits for an event from that thread before continuing. The other thread gets
signalled, copies the data from the temp buffer to a local buffer for
processing, signals the first thread to read the next scanline from the disk
and, while that is occuring, begins to process the data in its local buffer.
This is very fast on my windows machine on both Mono and Microsoft runtimes,
but on Mac + Mono it must be two orders of magnitude slower...no, I am not
exagerating. You can imagine some of the looks I got from people standing

Anyway, shall I prepare a small project that illustrates the algorithm? The
performance differences are so huge I have to believe there is something
fundamentally wrong "close to the metal". Hopefully its something that can
be fixed without too much fuss.

Anybody else see this kind of performance hit?:-(
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