Using OpenCL on Odroid-XU3 is slower than without OpenCL

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Hello, I use Odroid-XU3.
And I installed Opencv 3.0.0-rc1 on odroid-xu3 ubuntu 14.04.

I have two question.

First, In procedure installing opencv, there's no opencl sdk directory option.
I just check 'WITH_OPENCL' and etc.
But, Using OpenCL function is successful.
Why??????

Second, I tested OpenCV with OpenCL.
I referenced the website http://www.learnopencv.com/opencv-tra...
However, With OpenCL running time is 400ms and without OpenCL running time is 152ms.
I want to solve the weird problem.

Please help me
Thank you :)