diff options
Diffstat (limited to 'tools/cuda-ab/rt_probe.cu')
| -rw-r--r-- | tools/cuda-ab/rt_probe.cu | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/tools/cuda-ab/rt_probe.cu b/tools/cuda-ab/rt_probe.cu new file mode 100644 index 0000000..025301d --- /dev/null +++ b/tools/cuda-ab/rt_probe.cu @@ -0,0 +1,165 @@ +// SPDX-License-Identifier: BSD-3-Clause +/* + * rt_probe.cu - instrumented memcpy_roundtrip variant isolating the + * memset-phase D2H readback failure. + * + * Phases (argv[1]): + * "full" : H2D -> kernel -> D2H -> memset -> D2H (the original order) + * "sync" : same but cudaDeviceSynchronize() before the second D2H + * "memset" : memset -> D2H only (memset_probe shape, 3-buffer alloc) + * "rev" : memset -> D2H first, then H2D -> kernel -> D2H + * + * Forensics on the memset readback: first bad offset, byte histogram + * (0x5A / 0x00 / other), per-1MB chunk histogram, and the first 32 bytes. + * + * Build: nvcc -O2 --cudart=static -o rt_probe rt_probe.cu + */ + +#include <cstdio> +#include <cstdlib> +#include <cstdint> +#include <cstring> +#include <cuda_runtime.h> + +#define CHECK(x) \ + do { \ + cudaError_t e_ = (x); \ + if (e_ != cudaSuccess) { \ + printf("CUDA_ERROR %s at line %d\n", \ + cudaGetErrorString(e_), __LINE__); \ + printf("STATUS FAIL\n"); \ + return 1; \ + } \ + } while (0) + +#define MemsetByte 0x5A + +__global__ void bump(const float *in, float *out, int n) +{ + int i = blockIdx.x * blockDim.x + threadIdx.x; + + if (i < n) + out[i] = in[i] + 0.5f; +} + +static void memset_forensics(const unsigned char *h, size_t bytes, + const char *tag) +{ + size_t i, first_bad = (size_t)-1; + int bad = 0, n5a = 0, n00 = 0, nother = 0; + size_t chunk; + + for (i = 0; i < bytes; i++) { + if (h[i] == 0x5A) + n5a++; + else if (h[i] == 0x00) + n00++; + else + nother++; + if (h[i] != 0x5A) { + if (first_bad == (size_t)-1) + first_bad = i; + bad++; + } + } + printf("MEMSET-READ %s bad=%d first_bad=%zu n5a=%d n00=%d nother=%d\n", + tag, bad, first_bad, n5a, n00, nother); + printf("MEMSET-HEAD %s", tag); + for (i = 0; i < 32; i++) + printf(" %02x", h[i]); + printf("\n"); + if (first_bad != (size_t)-1) { + printf("MEMSET-ATBAD %s off=%zu:", tag, first_bad); + for (i = first_bad; i < first_bad + 16 && i < bytes; i++) + printf(" %02x", h[i]); + printf("\n"); + } + for (chunk = 0; chunk < bytes / (1u << 20); chunk++) { + size_t lo = chunk << 20, hi = lo + (1u << 20); + int c5a = 0, c00 = 0, cother = 0; + + for (i = lo; i < hi; i++) { + if (h[i] == 0x5A) + c5a++; + else if (h[i] == 0x00) + c00++; + else + cother++; + } + printf("MEMSET-MB %s mb=%zu 5a=%d 00=%d other=%d\n", + tag, chunk, c5a, c00, cother); + } +} + +int main(int argc, char **argv) +{ + const char *mode = argc > 1 ? argv[1] : "full"; + cudaDeviceProp prop; + const size_t bytes = 8u << 20; + const int n = (int)(bytes / sizeof(float)); + unsigned char *h_m; + float *h_in, *h_out; + float *d_in, *d_out; + unsigned char *d_m; + double csum = 0.0; + int bad = 0, i; + const int grid = (n + 255) / 256; + + setvbuf(stdout, NULL, _IONBF, 0); + + CHECK(cudaGetDeviceProperties(&prop, 0)); + printf("DEVICE %s cc=%d.%d sm=%d mem=%llu mode=%s\n", prop.name, + prop.major, prop.minor, prop.multiProcessorCount, + (unsigned long long)prop.totalGlobalMem, mode); + + h_in = (float *)malloc(bytes); + h_out = (float *)malloc(bytes); + h_m = (unsigned char *)malloc(bytes); + if (!h_in || !h_out || !h_m) + return 1; + + for (i = 0; i < n; i++) + h_in[i] = (float)(i % 1024) * 0.25f; + + CHECK(cudaMalloc(&d_in, bytes)); + CHECK(cudaMalloc(&d_out, bytes)); + CHECK(cudaMalloc(&d_m, bytes)); + printf("DPTRS d_in=%p d_out=%p d_m=%p\n", (void *)d_in, + (void *)d_out, (void *)d_m); + + if (!strcmp(mode, "memset") || !strcmp(mode, "rev")) { + /* memset phase first */ + CHECK(cudaMemset(d_m, MemsetByte, bytes)); + if (!strcmp(mode, "sync")) + CHECK(cudaDeviceSynchronize()); + CHECK(cudaMemcpy(h_m, d_m, bytes, cudaMemcpyDeviceToHost)); + memset_forensics(h_m, bytes, "early"); + } + + if (!strcmp(mode, "full") || !strcmp(mode, "sync") || + !strcmp(mode, "rev")) { + CHECK(cudaMemcpy(d_in, h_in, bytes, cudaMemcpyHostToDevice)); + bump<<<grid, 256>>>(d_in, d_out, n); + CHECK(cudaGetLastError()); + CHECK(cudaDeviceSynchronize()); + CHECK(cudaMemcpy(h_out, d_out, bytes, cudaMemcpyDeviceToHost)); + + for (i = 0; i < n; i++) { + if (h_out[i] != h_in[i] + 0.5f) + bad++; + csum += (double)h_out[i]; + } + printf("BUMP bad=%d csum=%.6f\n", bad, csum); + } + + if (!strcmp(mode, "full") || !strcmp(mode, "sync")) { + CHECK(cudaMemset(d_m, MemsetByte, bytes)); + if (!strcmp(mode, "sync")) + CHECK(cudaDeviceSynchronize()); + CHECK(cudaMemcpy(h_m, d_m, bytes, cudaMemcpyDeviceToHost)); + memset_forensics(h_m, bytes, "late"); + } + + printf("STATUS OK\n"); + return 0; +} |