Nsopenglcontext flushbuffer slowness

I’m on OSX using 0.9.2 and in my app doing a chain of post processing with shaders, bouncing textures back and forth between fbo’s (for blur). When I’m running tests at 1920x1080 everything seems to be stable and fine. However when I go to render at my actual size, 3840x1080, 50% of the time I build the app I get some extreme slowdown, 8-10fps. The other 50% of the time, it works flawlessly, 60fps or higher.

I ran the time profiler on my app and tracked it down to a call for nsopenglcontext flushbuffer, taking sometimes over 2000ms per draw call. When the app is running normally, flushbuffer only takes 20ms or so.

Why would this be happening only half the time? I can run and build the app without changing a thing and still see this behavior.

I’m also curious about where exactly in the depths of oF flush buffer is being called from.

Is this maybe a gpu driver issue? I’m on a 2011 iMac with an amd card fwiw. It’s not a big deal really, but it does seem odd, and thought I would see if anyone else has had an experience like this.