cudaMemcpyAsync的奇怪行为:1。cudaMemcpyKind没有区别。2.复制失败,但没有任何提示
我正在熟悉一个配备Pascal P100 GPU+Nvlink的新集群。我编写了一个乒乓程序来测试gpugpu和gpucpu的带宽以及点对点访问。(我知道cuda示例包含这样一个程序,但为了更好地理解,我想自己做。)Nvlink带宽似乎合理(约35 GB/s双向,理论最大值为40)。然而,在调试乒乓球时,我发现了一些奇怪的行为 首先,无论我指定什么样的cudaMemcpyKind,cudaMemcpyAsync都会成功,例如,如果cudaMemcpyAsync将内存从主机复制到设备,那么即使我将cudamemcpydevicetoost作为一种类型传递,它也会成功 其次,当主机内存未被页面锁定时,CUDAMEMCPIASYNC执行以下操作:cudaMemcpyAsync的奇怪行为:1。cudaMemcpyKind没有区别。2.复制失败,但没有任何提示,cuda,nvlink,cuda-uva,Cuda,Nvlink,Cuda Uva,我正在熟悉一个配备Pascal P100 GPU+Nvlink的新集群。我编写了一个乒乓程序来测试gpugpu和gpucpu的带宽以及点对点访问。(我知道cuda示例包含这样一个程序,但为了更好地理解,我想自己做。)Nvlink带宽似乎合理(约35 GB/s双向,理论最大值为40)。然而,在调试乒乓球时,我发现了一些奇怪的行为 首先,无论我指定什么样的cudaMemcpyKind,cudaMemcpyAsync都会成功,例如,如果cudaMemcpyAsync将内存从主机复制到设备,那么即使我将
- 将内存从主机复制到设备似乎成功(没有SEGFULTS或cuda运行时错误,并且数据传输正常)李>
- 将内存从设备复制到主机时会自动失败:不会发生segfault,memcpy返回cudaSuccess后cudaDeviceSynchronize,但检查数据会发现gpu上的数据未正确传输到主机
#include <stdio.h>
#include <cuda_runtime.h>
#include <stdlib.h>
#define gpuErrchk(ans) { gpuAssert((ans), __FILE__, __LINE__); }
inline void gpuAssert(cudaError_t code, const char *file, int line, bool abort=true)
{
if (code != cudaSuccess)
{
fprintf(stderr,"GPUassert: %s %s %d\n", cudaGetErrorString(code), file, line);
if (abort) exit(code);
}
}
__global__ void checkDataDevice( int* current, int* next, int expected_current_val, int n )
{
int tid = threadIdx.x + blockIdx.x*blockDim.x;
for( int i = tid; i < n; i += blockDim.x*gridDim.x )
{
if( current[i] != expected_current_val )
printf( "Error on device: expected = %d, current[%d] = %d\n"
, expected_current_val
, i
, current[i] );
// Increment the data so the next copy is properly tested
next[i] = current[i] + 1;
}
}
void checkDataHost( int* current, int* next, int expected_current_val, int n )
{
for( int i = 0; i < n; i++ )
{
if( current[i] != expected_current_val )
printf( "Error on host: expected = %d, current[%d] = %d\n"
, expected_current_val
, i
, current[i] );
// Increment the data so the next copy is properly tested
next[i] = current[i] + 1;
}
}
int main( int argc, char** argv )
{
bool pagelocked = true;
// invoking the executable with any additional argument(s) will turn off page locked memory, i.e.,
// Run with pagelocked memory: ./a.out
// Run with ordinary malloc'd memory: ./a.out jkfdlsja
if( argc > 1 )
pagelocked = false;
int copybytes = 1e8; // Ok to use int instead of size_t for 1e8.
cudaStream_t* stream = (cudaStream_t*)malloc( sizeof(cudaStream_t) );
cudaStreamCreate( stream );
int* srcHost;
int* dstHost;
int* srcDevice;
int* dstDevice;
cudaMalloc( (void**)&srcDevice, copybytes );
cudaMalloc( (void**)&dstDevice, copybytes );
if( pagelocked )
{
printf( "Using page locked memory\n" );
cudaMallocHost( (void**)&srcHost, copybytes );
cudaMallocHost( (void**)&dstHost, copybytes );
}
else
{
printf( "Using non page locked memory\n" );
srcHost = (int*)malloc( copybytes );
dstHost = (int*)malloc( copybytes );
}
for( int i = 0; i < copybytes/sizeof(int); i++ )
srcHost[i] = 1;
cudaMemcpyKind kinds[4];
kinds[0] = cudaMemcpyHostToDevice;
kinds[1] = cudaMemcpyDeviceToHost;
kinds[2] = cudaMemcpyHostToHost;
kinds[3] = cudaMemcpyDeviceToDevice;
// Test cudaMemcpyAsync in both directions,
// iterating through all "cudaMemcpyKinds" to verify
// that they don't matter.
int expected_current_val = 1;
for( int kind = 0; kind<4; kind++ )
{
// Host to device copy
cudaMemcpyAsync( dstDevice
, srcHost
, copybytes
, kinds[kind]
, *stream );
gpuErrchk( cudaDeviceSynchronize() );
checkDataDevice<<<56*8,256>>>( dstDevice
, srcDevice
, expected_current_val
, copybytes/sizeof(int) );
expected_current_val++;
// Device to host copy
cudaMemcpyAsync( dstHost
, srcDevice
, copybytes
, kinds[kind]
, *stream );
gpuErrchk( cudaDeviceSynchronize() );
checkDataHost( dstHost
, srcHost
, expected_current_val
, copybytes/sizeof(int) );
expected_current_val++;
}
free( stream );
cudaFree( srcDevice );
cudaFree( dstDevice );
if( pagelocked )
{
cudaFreeHost( srcHost );
cudaFreeHost( dstHost );
}
else
{
free( srcHost );
free( dstHost );
}
return 0;
}
#包括
#包括
#包括
#定义gpuerchk(ans){gpuAssert((ans),_文件_,_行__)}
内联void gpuAssert(cudaError\u t代码,const char*文件,int行,bool abort=true)
{
如果(代码!=cudaSuccess)
{
fprintf(标准,“GPUassert:%s%s%d\n”,cudaGetErrorString(代码)、文件、行);
如果(中止)退出(代码);
}
}
__全局无效checkDataDevice(int*当前,int*下一步,int预期值,int n)
{
int tid=threadIdx.x+blockIdx.x*blockDim.x;
对于(inti=tid;i1)
pagelocked=false;
int copybytes=1e8;//确定对1e8使用int而不是size\u t。
cudaStream_t*stream=(cudaStream_t*)malloc(sizeof(cudaStream_t));
cudaStreamCreate(流);
int*srcHost;
int*dstHost;
int*src设备;
int*dst设备;
cudamaloc((void**)和srcDevice,copybytes);
cudamaloc((void**)和dstDevice,copybytes);
如果(页面锁定)
{
printf(“使用页面锁定内存\n”);
cudaMallocHost((void**)和srcHost,copybytes);
cudaMallocHost((void**)和dstHost,copybytes);
}
其他的
{
printf(“使用非页面锁定内存\n”);
srcHost=(int*)malloc(copybytes);
DSTOST=(int*)malloc(copybytes);
}
对于(int i=0;i 对于(int kind=0;kind当CUDA代码出现问题时,我强烈建议使用严格(==检查每个呼叫返回代码)
你的错误检查是有缺陷的,这些缺陷导致了你的一些困惑
首先,在页面锁定的情况下,给定的(映射的)指针在主机和设备上都是可访问/有效的。因此,每个可能的方向枚举(H2D、D2H、D2D、H2H)都是合法和有效的。因此,不会返回错误,复制操作成功
在非页面锁定的情况下,上述情况不正确,因此一般来说,指示的传输方向最好与从指针检查的隐含传输方向匹配。如果不匹配,则cudaMemcpyAsync
将返回错误代码(cudaErrorInvalidValue
==11)。在您的情况下,您忽略了此错误结果。如果您有足够的耐心,您可以通过使用cuda memcheck
(当您在使用CUDA代码时,另一件好事是)或者只需进行适当、严格的错误检查
当cudaMemcpyAsync
操作指示失败时,操作未成功完成,因此数据未被复制,并且您的数据检查指示不匹配。希望这不会令人惊讶,因为预期的复制操作会起作用
$ cat t153.cu
#include <stdio.h>
#include <stdlib.h>
#define gpuErrchk(ans) { gpuAssert((ans), __FILE__, __LINE__); }
inline void gpuAssert(cudaError_t code, const char *file, int line, bool abort=true)
{
if (code != cudaSuccess)
{
fprintf(stderr,"GPUassert: %s %s %d\n", cudaGetErrorString(code), file, line);
if (abort) exit(code);
}
}
__global__ void checkDataDevice( int* current, int* next, int expected_current_val, int n )
{
int tid = threadIdx.x + blockIdx.x*blockDim.x;
for( int i = tid; i < n; i += blockDim.x*gridDim.x )
{
if( current[i] != expected_current_val )
printf( "Error on device: expected = %d, current[%d] = %d\n"
, expected_current_val
, i
, current[i] );
// Increment the data so the next copy is properly tested
next[i] = current[i] + 1;
}
}
void checkDataHost( int* current, int* next, int expected_current_val, int n )
{
for( int i = 0; i < n; i++ )
{
if( current[i] != expected_current_val ){
printf( "Error on host: expected = %d, current[%d] = %d\n"
, expected_current_val
, i
, current[i] );
exit(0);}
// Increment the data so the next copy is properly tested
next[i] = current[i] + 1;
}
}
int main( int argc, char** argv )
{
bool pagelocked = true;
// invoking the executable with any additional argument(s) will turn off page locked memory, i.e.,
// Run with pagelocked memory: ./a.out
// Run with ordinary malloc'd memory: ./a.out jkfdlsja
if( argc > 1 )
pagelocked = false;
int copybytes = 1e8; // Ok to use int instead of size_t for 1e8.
cudaStream_t* stream = (cudaStream_t*)malloc( sizeof(cudaStream_t) );
cudaStreamCreate( stream );
int* srcHost;
int* dstHost;
int* srcDevice;
int* dstDevice;
cudaMalloc( (void**)&srcDevice, copybytes );
cudaMalloc( (void**)&dstDevice, copybytes );
if( pagelocked )
{
printf( "Using page locked memory\n" );
cudaMallocHost( (void**)&srcHost, copybytes );
cudaMallocHost( (void**)&dstHost, copybytes );
}
else
{
printf( "Using non page locked memory\n" );
srcHost = (int*)malloc( copybytes );
dstHost = (int*)malloc( copybytes );
}
for( int i = 0; i < copybytes/sizeof(int); i++ )
srcHost[i] = 1;
cudaMemcpyKind kinds[4];
kinds[0] = cudaMemcpyHostToDevice;
kinds[1] = cudaMemcpyDeviceToHost;
kinds[2] = cudaMemcpyHostToHost;
kinds[3] = cudaMemcpyDeviceToDevice;
// Test cudaMemcpyAsync in both directions,
// iterating through all "cudaMemcpyKinds" to verify
// that they don't matter.
int expected_current_val = 1;
for( int kind = 0; kind<4; kind++ )
{
// Host to device copy
cudaMemcpyAsync( dstDevice
, srcHost
, copybytes
, kinds[kind]
, *stream );
gpuErrchk( cudaDeviceSynchronize() );
checkDataDevice<<<56*8,256>>>( dstDevice
, srcDevice
, expected_current_val
, copybytes/sizeof(int) );
expected_current_val++;
// Device to host copy
cudaMemcpyAsync( dstHost
, srcDevice
, copybytes
, kinds[kind]
, *stream );
gpuErrchk( cudaDeviceSynchronize() );
checkDataHost( dstHost
, srcHost
, expected_current_val
, copybytes/sizeof(int) );
expected_current_val++;
}
free( stream );
cudaFree( srcDevice );
cudaFree( dstDevice );
if( pagelocked )
{
cudaFreeHost( srcHost );
cudaFreeHost( dstHost );
}
else
{
free( srcHost );
free( dstHost );
}
return 0;
}
$ nvcc -arch=sm_61 -o t153 t153.cu
$ cuda-memcheck ./t153 a
========= CUDA-MEMCHECK
Using non page locked memory
========= Program hit cudaErrorInvalidValue (error 11) due to "invalid argument" on CUDA API call to cudaMemcpyAsync.
========= Saved host backtrace up to driver entry point at error
========= Host Frame:/usr/lib/x86_64-linux-gnu/libcuda.so.1 [0x2ef423]
========= Host Frame:./t153 [0x489a3]
========= Host Frame:./t153 [0x2e11]
========= Host Frame:/lib/x86_64-linux-gnu/libc.so.6 (__libc_start_main + 0xf5) [0x21ec5]
========= Host Frame:./t153 [0x2a49]
=========
Error on host: expected = 2, current[0] = 0
========= ERROR SUMMARY: 1 error
$