clfinish is taking more time than kernel execution time

Hi All,

I am working on a application where every millisec counts. Please refer to the below data.

Time clFinish 40889 micro seconds

OpenCl Execution time is: 32.301 milliseconds

Time ReadBuffer 234

Time clFinish 41386 micro seconds

OpenCl Execution time is: 31.889 milliseconds

Time ReadBuffer 331

The kernel execution above is taking ~32msec, I have printed this using clGetEventProfilingInfo. But when I check the clfinish time it is close to ~40msec.

As you can see above here there is a gap of 8msec from clfinish and kernel execution time. Even in profile.mon file the kernel execution status is close to 32msec.

Can you please help me understand where I am loosing 8msec, as per my understanding the clfinish time should equivalent to that of the Kernel execution time as I dont have any pending Queues in commandQueue.

Thanks in advance.