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Re: Enabling Multithreaded GL - any purpose with predominantly Quartz Composer driven code?

So I did some very quick tests with a few serialized core image kernels within QC compositions, and set up a way to turn on/off multithreaded GL. 

Basically my pipeline consisted of

video input patch with its own QCRenderer.
| 
QCImage Out
|  
CMYK Halftone patch with its own QCRenderer
|
QCImage Out
|
Largish QC Patch with custom CIKernels with many queues etc with its own QCRenderer
|
 QCImage output
|
QC patch with Billboard display with its own QCRenderer

I did in fact see slightly poorer performance with MP openGL enabled (assuming I did things correctly, which I believe I did), on the order of 15%/20% less FPS on average. Im not 100% convinced yet, so ill keep coming back to it as I add features. Should I find anything interesting I will report it. Anyway.. sorry for the extraneous traffic. Im curious why things get slower though, basic overhead of keeping the thread state synchronized and not stepping on toes?

FYI this was the method I added to my app to enable/disable should others want to test as well.

-(IBAction) enableMPGL:(id)sender
{
CGLError cglError = kCGLNoError;


// returns 0 or a 1 via NSButton toggle
if([sender state])
{
// Try and enable multithreaded openGL! WOooWW oWWWoo WEEE WWooooow
cglError = CGLEnable( [v001GLContext CGLContextObj], kCGLCEMPEngine);


if ( cglError != kCGLNoError )
{
// oops! not happening fuckers.
NSLog(@"Multithreaded  OpenGL was not properly enabled");
}
else
{
NSLog(@"Enabled Multhreaded OpenGL sucessfully");
}
}
else
{
cglError = CGLDisable([v001GLContext CGLContextObj], kCGLCEMPEngine);


if ( cglError != kCGLNoError )
{
// oops! not happening fuckers.
NSLog(@"Multithreaded  OpenGL was not properly disabled");
}
else
{
NSLog(@"Disabled Multhreaded OpenGL sucessfully");
}
}
}


On Feb 19, 2008, at 4:28 PM, vade wrote:

I don't know of any appropriate cases where this would help performance, but I've seen a few instances where it adversely affected performance in a negative way (i.e. 60fps compositions dropping to 20fps or worse).  As with all optimization, be sure to profile exhaustively to make sure what you're doing actually helps rather than hinders.

Here's a quick doc I found that may help guide you: http://developer.apple.com/technotes/tn2006/tn2085.html#TNTAG7

When/If you find where this option helps, please let me know; I'm curious about where it's appropriate as well (in more concrete ways than the doc outlines) :)

--
[ christopher wright ]
email@hidden
http://kineme.net/
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References: 
 >Enabling Multithreaded GL - any purpose with predominantly Quartz Composer driven code? (From: vade <email@hidden>)
 >Re: Enabling Multithreaded GL - any purpose with predominantly Quartz Composer driven code? (From: Christopher Wright <email@hidden>)
 >Re: Enabling Multithreaded GL - any purpose with predominantly Quartz Composer driven code? (From: vade <email@hidden>)



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