title: opencl long kernel execution time
body: <p>I implement some image processing on opencl on GPU. On host program i launch this kernel 4 times, total time of this about 13 ms(on AMD profiler), it is good result, i think, but if i measure kernel execution time on host by QueryPerformanceTimer it shows about 26 ms. clEnqueueNDRangeKernel execution time smaller than 1 ms. Where is 26-13 ms ? how fix it? i launch it on GPU 1: AMD Radeon HD 6900 Series, using AMD SDK 3.0. If i launch kernel once, but in kernel i add 4 times cycle resulte is same.</p>