llglsandbox.cpp

			gGL.getTexUnit(0)->bindManual(LLTexUnit::TT_TEXTURE, source[i]);
			buff->drawArrays(LLRender::TRIANGLES, 0, 12);
			dest[i].flush();
		}
		
		//wait for current batch of copies to finish
		if (busted_finish)
		{
			//read a pixel off the last target since some drivers seem to ignore glFinish
			dest[count-1].bindTarget();
			U32 pixel = 0;
			glReadPixels(0,0,1,1,GL_RGBA, GL_UNSIGNED_BYTE, &pixel);
			dest[count-1].flush();
		}
		else
		{
			glFinish();
		}

		F32 time = timer.getElapsedTimeF32();

		if (c >= 0) // <-- ignore the first sample as it tends to be artificially slow
		{ 
			//store result in gigabytes per second
			F32 gb = (F32) ((F64) (res*res*8*count))/(1000000000);

			F32 gbps = gb/time;

			if (!gGLManager.mHasTimerQuery && !busted_finish && gbps > 128.f)
			{ //unrealistically high bandwidth for a card without timer queries, glFinish is probably ignored
				busted_finish = true;
				LL_INFOS() << "GPU BENCHMARK DETECTED GL DRIVER WITH NOT SO MUCH WORKING glFinish." << LL_ENDL;
			}
			else
			{
				LL_INFOS() << "GPU BENCHMARK ESTIMATE." << gbps << " Gbps" << LL_ENDL;
				results.push_back(gbps);
			}		
		}
	}

	gBenchmarkProgram.unbind();

	if (gGLManager.mHasTimerQuery)
	{
		LLGLSLShader::finishProfile(false);
	}

	LLImageGL::deleteTextures(count, source);

	std::sort(results.begin(), results.end());

	F32 gbps = results[results.size()/2];

	LL_INFOS() << "Memory bandwidth is " << llformat("%.3f", gbps) << "GB/sec according to CPU timers" << LL_ENDL;
  
#if LL_DARWIN
    if (gbps > 512.f)
    { 
        LL_INFOS() << "Memory bandwidth is improbably high and likely incorrect." << LL_ENDL;
        //OSX is probably lying, discard result
        gbps = -1.f;
    }
#endif

	if (gGLManager.mHasTimerQuery)
	{
		F32 ms = gBenchmarkProgram.mTimeElapsed/1000000.f;
		F32 seconds = ms/1000.f;

		F64 samples_drawn = res*res*count*samples;
		F32 samples_sec = (samples_drawn/1000000000.0)/seconds;
		gbps = samples_sec*8;

		LL_INFOS() << "Memory bandwidth is " << llformat("%.3f", gbps) << "GB/sec according to ARB_timer_query" << LL_ENDL;
	}
	else
	{
		LL_INFOS() << "ARB_timer_query unavailable." << LL_ENDL;
	}

	return gbps;
}