[Mono-osx] Horrible performance on Mac, need advice.
lionel.keene at gmail.com
Mon Jul 20 16:51:24 EDT 2009
Hi Geoff, thanks for the reply.
I no longer believe the disk IO mechanism is at fault. I've written a
super-simple little app that replicates my strategy in single/multi-threaded
modes and performance on the Mac is fine. It's looking more and more like it
may be the drawing (I'm using GDI+ everywhere).
What I'm doing (in an effort to gain fast performance) is to instantiate the
Bitmap objects I'll be using at application startup as follows:
// Instantiate Bitmap object and pinned array:
PixelFormat myPixelFormat = PixelFormat.Format32bppArgb;
pixelFormatSize = Image.GetPixelFormatSize(myPixelFormat) / 8;
stride = this.CanvasWidth * pixelFormatSize;
Channel1BitmapBytes = new byte[stride * this.CanvasHeight];
handle = GCHandle.Alloc(Channel1BitmapBytes, GCHandleType.Pinned); // Pin
IntPtr channel1PTR =
Channel1Bitmap = new Bitmap(this.CanvasWidth, this.CanvasHeight, stride,
// ...later on (in Paint event handler for example)...
Graphics grafix = Graphics.FromImage(Channel1Bitmap);
"Channel1BitmapBytes" is a declared globally (within the context of "this")
and, because the array is pinned, I can write to it in multi-threaded
fashion. On Windows this works very well and I get realtime graphics
performance. Could the above be the culprit on OSX? Thanks for any feedback!
Geoff Norton-2 wrote:
> I presumse you're doing a lot of Graphics.FromHwnd (handle); all over
> the place, this is a huge performance problem on the mac. Try to
> coalesce your graphics updates intstead of doing a ton of one-offs.
> On 20-Jul-09, at 4:29 PM, LKeene wrote:
>> Hello again folks.
>> As the title says, I'm getting GAWD-AWFUL performance with my app when
>> running on mono 126.96.36.199 + Mac OS X. The exact same binary runs in
>> real-time on Mono + Windows. Mac performance is literally dozens of
>> 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
>> disk, processed via some mathematical operations, then rendered on
>> 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
>> This is very fast on my windows machine on both Mono and Microsoft
>> 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
>> Anyway, shall I prepare a small project that illustrates the
>> algorithm? The
>> performance differences are so huge I have to believe there is
>> 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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