Tesla K20m主要参数

Total amount of global memory:                 4800 MBytes (5032706048 bytes)
Total amount of constant memory:               64KB(65536 bytes)
Total amount of shared memory per block:       48KB(49152 bytes)‬
Total number of registers available per block: 65536
Maximum number of threads per multiprocessor:  2048 (每个SM最多可处理2048个线程)
Maximum number of threads per block:           1024
Max dimension size of a thread block (x,y,z):  (1024, 1024, 64)
Max dimension size of a grid size    (x,y,z):  (2147483647, 65535, 65535)
 (13) Multiprocessors, (192) CUDA Cores/MP:    2496 CUDA Cores (共13个SM, 每个SM有192个SP, 一共13*192=2496个SP， CUDA Cores也就是SP)

每个GPU结点:

• 共13个SM, 每个SM有192个SP, 一共13*192=2496个SP;
• 一个SM中最多有2048个线程，即一个SM最多2048/32=64个线程束Warp
• 一个block最多1024个线程，
• 每个block最多65536个寄存器可用

deviceQuery查询结果：

Device 0: "Tesla K20m"
  CUDA Driver Version / Runtime Version          6.5 / 6.0
  CUDA Capability Major/Minor version number:    3.5
  Total amount of global memory:                 4800 MBytes (5032706048 bytes)
  (13) Multiprocessors, (192) CUDA Cores/MP:     2496 CUDA Cores (13个SM，每个SM192个SP)
  GPU Clock rate:                                706 MHz (0.71 GHz)
  Memory Clock rate:                             2600 Mhz
  Memory Bus Width:                              320-bit
  L2 Cache Size:                                 1310720 bytes
  Maximum Texture Dimension Size (x,y,z)         1D=(65536), 2D=(65536, 65536), 3D=(4096, 4096, 4096)
  Maximum Layered 1D Texture Size, (num) layers  1D=(16384), 2048 layers
  Maximum Layered 2D Texture Size, (num) layers  2D=(16384, 16384), 2048 layers
  Texture alignment:                             512 bytes
  Total amount of constant memory:               64KB (65536 bytes)
  Total amount of shared memory per block:       48KB (49152 bytes)
  Total number of registers available per block: 65536
  Warp size:                                     32
  Maximum number of threads per multiprocessor:  2048 
  Maximum number of threads per block:           1024
  Max dimension size of a thread block (x,y,z): (1024, 1024, 64)
  Max dimension size of a grid size    (x,y,z): (2147483647, 65535, 65535)
  Maximum memory pitch:                          2147483647 bytes （显存访问时对齐时的pitch的最大值）
  Concurrent copy and kernel execution:          Yes with 2 copy engine(s)
  Run time limit on kernels:                     No
  Integrated GPU sharing Host Memory:            No
  Support host page-locked memory mapping:       Yes
  Alignment requirement for Surfaces:            Yes
  Device has ECC support:                        Enabled
  Device supports Unified Addressing (UVA):      Yes
  Device PCI Bus ID / PCI location ID:           6 / 0
  Compute Mode:
     < Default (multiple host threads can use ::cudaSetDevice() with device simultaneously) >

Device 1: "Tesla K20m"
  CUDA Driver Version / Runtime Version          6.5 / 6.0
  CUDA Capability Major/Minor version number:    3.5
  Total amount of global memory:                 4800 MBytes (5032706048 bytes)
  (13) Multiprocessors, (192) CUDA Cores/MP:     2496 CUDA Cores
  GPU Clock rate:                                706 MHz (0.71 GHz)
  Memory Clock rate:                             2600 Mhz
  Memory Bus Width:                              320-bit
  L2 Cache Size:                                 1310720 bytes
  Maximum Texture Dimension Size (x,y,z)         1D=(65536), 2D=(65536, 65536), 3D=(4096, 4096, 4096)
  Maximum Layered 1D Texture Size, (num) layers  1D=(16384), 2048 layers
  Maximum Layered 2D Texture Size, (num) layers  2D=(16384, 16384), 2048 layers
  Total amount of constant memory:               65536 bytes
  Total amount of shared memory per block:       49152 bytes
  Total number of registers available per block: 65536
  Warp size:                                     32
  Maximum number of threads per multiprocessor:  2048
  Maximum number of threads per block:           1024
  Max dimension size of a thread block (x,y,z): (1024, 1024, 64)
  Max dimension size of a grid size    (x,y,z): (2147483647, 65535, 65535)
  Maximum memory pitch:                          2147483647 bytes
  Texture alignment:                             512 bytes
  Concurrent copy and kernel execution:          Yes with 2 copy engine(s)
  Run time limit on kernels:                     No
  Integrated GPU sharing Host Memory:            No
  Support host page-locked memory mapping:       Yes
  Alignment requirement for Surfaces:            Yes
  Device has ECC support:                        Enabled
  Device supports Unified Addressing (UVA):      Yes
  Device PCI Bus ID / PCI location ID:           132 / 0
  Compute Mode:
     < Default (multiple host threads can use ::cudaSetDevice() with device simultaneously) >
> Peer access from Tesla K20m (GPU0) -> Tesla K20m (GPU1) : No
> Peer access from Tesla K20m (GPU1) -> Tesla K20m (GPU0) : No

deviceQuery, CUDA Driver = CUDART, CUDA Driver Version = 6.5, CUDA Runtime Version = 6.0, NumDevs = 2, Device0 = Tesla K20m, Device1 = Tesla K20m
Result = PASS

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nvprof的使用：

首先保证使用nvcc编译器将源程序编译为可执行程序

接着执行命令：

nvprof ./gpu-fmm

profiling result中显示的是kernel执行的time情况, api calls则显示的是程序调用的api所耗费的time情况,
一般对kernel进行分析时，看profiling result中的结果。
此外，还可以测试程序的其他性能参数：

achieved_occupancy参数：每个sm在每个cycle能够达到的最大activewarp 占总warp的比例。

nvprof --metrics achieved_occupancy ./gpu-fmm

gld_throughput: global load throughput (查看memory 的throughput)

nvprof --metrics gld_throughput ./gpu-fmm

gld_efficiency: global memory loadefficiency: device memory bandwidth的使用率

nvprof –metrics gld_efficiency ./ gpu-fmm

nvprof查询bank冲突:

nvprof --events shared_ld_bank_conflict,shared_st_bank_conflict ./gpu-fmm