What is the difference between SVM and CL::buffer

OpenCL
1

hi,

I am not sure if the topic tittle is the ritgh one. I used to do the following procces with openCL on Android.

  1. i create the platform,queu,devive. Create all my cl::buffer and compile all the kernel at the start of my application.

  2. i get picture from my camera and send the byte data using JNI jbyteArray =>((uint8_t*)inPtr) to my c++ function.

  3. i get the (uint8_t*)inPtr pointer than i use cl::buffer to feed the buffer with the camera picture data, using :
    bufferNV21 = cl::Buffer(gContext, CL_MEM_READ_ONLY|CL_MEM_USE_HOST_PTR , isize*sizeof(cl_uchar), inPtr , NULL); this take less than 1ms.

  4. i process my kernel NV21toRGB than i do some staff with my output buffer.

  5. i use enqueueMapBuffer to point the Buffer,buf, to my local program memory and that wil be used by pthread CPU processing. take less than 2ms

  6. than i copy back the CPU result to the GPU buffer doing:
    bufferligne = cl::Buffer(gContext, CL_MEM_USE_HOST_PTR, (1024*1024)*sizeof(cl_uchar4), buf, NULL); // remplace enqueueWriteBuffer.
    this take less than 3ms

  7. do some kernel on bufferligne cl::buffer

  8. then send back the GPU buffer(bufferMMM) to Java out bitmap using
    gQueue.enqueueReadBuffer(bufferMMM, CL_TRUE, 0, osize*sizeof(cl_uchar4), out, 0, &arraySecondEvent); // pour openCL
    this last part take between 3 and 5ms, depends. Sometime less.

So what should i change if i want to use SVM. Change at step 3,5,7 or 8.

And what does SVM that cl::buffer does not. I would like to anderstand Why to use SVM. Where are the improvement. Because that i am sure is that i lost a lot of time not really in the kernel speed, i improved the speed by using on the kernel .cl file

#pragma OPENCL EXTENSION cl_khr_priority_hints : enable // accelere openCL queue driver
#pragma OPENCL EXTENSION CL_QUEUE_PRIORITY_HIGH_KHR : enable

and on the .cpp

// Optional extension support
#define CL_HPP_USE_IL_KHR
#define CL_HPP_USE_CL_SUB_GROUPS_KHR
#define CL_HPP_OPENCL_API_WRAPPER

But i lost a lot of time using CPU pthread on the xiaomi. So it is may be why SVM could improve. I am not sure if it is an OpenCL problem or Pthread problem on the médiatek processor.

regards and thanks for help.