[英]“Zero copy” is slower in my OpenCL/Cloo(C#) program than non-zero copy
這可能只是一個問題,.NET框架分配的內存對象未正確進行頁面對齊,但是我看不到為什么零拷貝對我來說比非零拷貝要慢。
我將在此問題中內聯代碼,但完整的源代碼可以在這里看到: https : //github.com/kwende/ClooMatrixMultiply/blob/master/GiantMatrixOnGPU/GPUMatrixMultiplier.cs 。
由於這是我首次嘗試實現零拷貝工作,因此我編寫了一個簡單的矩陣乘法示例。 我首先初始化我的OpenCL對象:
private void Initialize()
{
// get the intel integrated GPU
_integratedIntelGPUPlatform = ComputePlatform.Platforms.Where(n => n.Name.Contains("Intel")).First();
// create the compute context.
_context = new ComputeContext(
ComputeDeviceTypes.Gpu, // use the gpu
new ComputeContextPropertyList(_integratedIntelGPUPlatform), // use the intel openCL platform
null,
IntPtr.Zero);
// the command queue is the, well, queue of commands sent to the "device" (GPU)
_commandQueue = new ComputeCommandQueue(
_context, // the compute context
_context.Devices[0], // first device matching the context specifications
ComputeCommandQueueFlags.None); // no special flags
string kernelSource = null;
using (StreamReader sr = new StreamReader("kernel.cl"))
{
kernelSource = sr.ReadToEnd();
}
// create the "program"
_program = new ComputeProgram(_context, new string[] { kernelSource });
// compile.
_program.Build(null, null, null, IntPtr.Zero);
_kernel = _program.CreateKernel("ComputeMatrix");
}
...這僅在我的代碼尚未初始化的情況下執行一次。 然后我進入主體。 對於非零副本,我執行以下操作:
public float[] MultiplyMatrices(float[] matrix1, float[] matrix2,
int matrix1Height, int matrix1WidthMatrix2Height, int matrix2Width)
{
if (!_initialized)
{
Initialize();
_initialized = true;
}
ComputeBuffer<float> matrix1Buffer = new ComputeBuffer<float>(_context,
ComputeMemoryFlags.ReadOnly | ComputeMemoryFlags.CopyHostPointer,
matrix1);
_kernel.SetMemoryArgument(0, matrix1Buffer);
ComputeBuffer<float> matrix2Buffer = new ComputeBuffer<float>(_context,
ComputeMemoryFlags.ReadOnly | ComputeMemoryFlags.CopyHostPointer,
matrix2);
_kernel.SetMemoryArgument(1, matrix2Buffer);
float[] ret = new float[matrix1Height * matrix2Width];
ComputeBuffer<float> retBuffer = new ComputeBuffer<float>(_context,
ComputeMemoryFlags.ReadWrite | ComputeMemoryFlags.CopyHostPointer,
ret);
_kernel.SetMemoryArgument(2, retBuffer);
_kernel.SetValueArgument<int>(3, matrix1WidthMatrix2Height);
_kernel.SetValueArgument<int>(4, matrix2Width);
_commandQueue.Execute(_kernel,
new long[] { 0 },
new long[] { matrix2Width, matrix1Height },
null, null);
unsafe
{
fixed (float* retPtr = ret)
{
_commandQueue.Read(retBuffer,
false, 0,
ret.Length,
new IntPtr(retPtr),
null);
_commandQueue.Finish();
}
}
matrix1Buffer.Dispose();
matrix2Buffer.Dispose();
retBuffer.Dispose();
return ret;
}
您可以看到我如何為所有ComputeBuffer分配顯式設置CopyHostPointer。 執行良好。
然后,我進行以下調整(包括設置“ UseHostPointer”並調用Map / Unmap而不是Read):
public float[] MultiplyMatricesZeroCopy(float[] matrix1, float[] matrix2,
int matrix1Height, int matrix1WidthMatrix2Height, int matrix2Width)
{
if (!_initialized)
{
Initialize();
_initialized = true;
}
ComputeBuffer<float> matrix1Buffer = new ComputeBuffer<float>(_context,
ComputeMemoryFlags.ReadOnly | ComputeMemoryFlags.CopyHostPointer,
matrix1);
_kernel.SetMemoryArgument(0, matrix1Buffer);
ComputeBuffer<float> matrix2Buffer = new ComputeBuffer<float>(_context,
ComputeMemoryFlags.ReadOnly | ComputeMemoryFlags.CopyHostPointer,
matrix2);
_kernel.SetMemoryArgument(1, matrix2Buffer);
float[] ret = new float[matrix1Height * matrix2Width];
ComputeBuffer<float> retBuffer = new ComputeBuffer<float>(_context,
ComputeMemoryFlags.ReadWrite | ComputeMemoryFlags.UseHostPointer,
ret);
_kernel.SetMemoryArgument(2, retBuffer);
_kernel.SetValueArgument<int>(3, matrix1WidthMatrix2Height);
_kernel.SetValueArgument<int>(4, matrix2Width);
_commandQueue.Execute(_kernel,
new long[] { 0 },
new long[] { matrix2Width, matrix1Height },
null, null);
IntPtr retPtr = _commandQueue.Map(
retBuffer,
false,
ComputeMemoryMappingFlags.Read,
0,
ret.Length, null);
_commandQueue.Unmap(retBuffer, ref retPtr, null);
_commandQueue.Finish();
matrix1Buffer.Dispose();
matrix2Buffer.Dispose();
retBuffer.Dispose();
return ret;
}
時機說明了一切。 我的程序將其吐出:
CPU矩陣乘法:1178.5ms
GPU矩陣乘法(復制):115.1毫秒
GPU矩陣乘法(零復制):174.1ms
GPU(含副本)的速度提高了10.23892倍。
GPU(零副本)速度為6.769098x。
...所以零拷貝比較慢。
多虧了huseyin tugrul buyukisik,我才知道發生了什么。
我需要更新我的英特爾驅動程序。 一旦完成此操作,零副本的速度就會快得多。
為了后代,這是零復制代碼的最終版本:
public float[] MultiplyMatricesZeroCopy(float[] matrix1, float[] matrix2,
int matrix1Height, int matrix1WidthMatrix2Height, int matrix2Width)
{
if (!_initialized)
{
Initialize();
_initialized = true;
}
ComputeBuffer<float> matrix1Buffer = new ComputeBuffer<float>(_context,
ComputeMemoryFlags.ReadOnly | ComputeMemoryFlags.CopyHostPointer,
matrix1);
_kernel.SetMemoryArgument(0, matrix1Buffer);
ComputeBuffer<float> matrix2Buffer = new ComputeBuffer<float>(_context,
ComputeMemoryFlags.ReadOnly | ComputeMemoryFlags.CopyHostPointer,
matrix2);
_kernel.SetMemoryArgument(1, matrix2Buffer);
float[] ret = new float[matrix1Height * matrix2Width];
GCHandle handle = GCHandle.Alloc(ret, GCHandleType.Pinned);
ComputeBuffer<float> retBuffer = new ComputeBuffer<float>(_context,
ComputeMemoryFlags.UseHostPointer,
ret);
_kernel.SetMemoryArgument(2, retBuffer);
_kernel.SetValueArgument<int>(3, matrix1WidthMatrix2Height);
_kernel.SetValueArgument<int>(4, matrix2Width);
_commandQueue.Execute(_kernel,
new long[] { 0 },
new long[] { matrix2Width, matrix1Height },
null, null);
IntPtr retPtr = _commandQueue.Map(
retBuffer,
true,
ComputeMemoryMappingFlags.Read,
0,
ret.Length, null);
_commandQueue.Unmap(retBuffer, ref retPtr, null);
//_commandQueue.Finish();
matrix1Buffer.Dispose();
matrix2Buffer.Dispose();
retBuffer.Dispose();
handle.Free();
return ret;
}
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