Timer resolution in OpenCL profiling - parallel-processing

Question

I need some clarification on timer resolution. I'm trying to learn profiling in openCL. I have reduction algorithm implemented in OpenCL and want to measure the execution kernel time by getting the total elapsed time in the code given below. I ran this code on different devices and here are the results:
On CPU -- AMD FX 770K
Total time = 352,855,601
CL_DEVICE_PROFILING_TIMER_RESOLUTION = 69 ns
On GPU -- AMD Radeon R7 240
Total time = 172,297
CL_DEVICE_PROFILING_TIMER_RESOLUTION = 1 ns
On another GPU -- GeForce GT 610
Total time = 1,725,504
CL_DEVICE_PROFILING_TIMER_RESOLUTION = 1000 ns
The "Total time" given above is in actual nanoseconds? or I need to divide them by the time resolution to get the actual execution time? How the timer resolution can help us?
Here is a part of the code:
/* Enqueue kernel */
err = clEnqueueNDRangeKernel(queue, kernel[i], 1, NULL, &global_size,
&local_size, 0, NULL, &prof_event);
if (err < 0) {
perror("Couldn't enqueue the kernel");
exit(1);
}
/* Finish processing the queue and get profiling information */
clFinish(queue);
clGetEventProfilingInfo(prof_event, CL_PROFILING_COMMAND_START,
sizeof(time_start), &time_start, NULL);
clGetEventProfilingInfo(prof_event, CL_PROFILING_COMMAND_END,
sizeof(time_end), &time_end, NULL);
total_time = time_end - time_start;
printf("Total time = %lu\n\n", total_time);

Answer 1

The specification is pretty clear on this: "current device time counter in
nanoseconds"
The times are always in nanoseconds. The resolution query is so you can find out how accurate the data is. For example, given the measurements and resolutions you posted, you can deduce the the error margin of the measure:
AMD FX 770K:
Measured: 352,855,601 ± 69 ns
Actual: 352,855,532 - 352,855,670
AMD Radeon R7 240:
Measured: 172,297 ± 1 ns
Actual: 172,296 - 172,298
GeForce GT 610:
Measured: 1,725,504 ± 1000 ns
Actual: 1,724,504 - 1,726,504