feat(test): 添加 pwritev 性能测试程序

Author: mistcoversmyeyes

user/apps/c_unitest/test_pwritev_perf.c

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+// ==============================================
+//
+//              本文件用于测试系统调用 pwritev 在使用
+//              大量小块数据写入时的性能表现。
+//              重点测试 user_access_len() 函数的开销
+//
+// ==============================================
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <unistd.h>
+#include <time.h>
+#include <string.h>
+#include <errno.h>
+
+#define TEST_FILE "pwritev_test.dat"
+#define NUM_IOV 1000
+#define SMALL_DATA_SIZE 64
+#define TOTAL_ITERATIONS 100
+
+// 测试用的小数据块
+struct test_iovec {
+    struct iovec iov[NUM_IOV];
+    char data[NUM_IOV][SMALL_DATA_SIZE];
+};
+
+// 初始化测试数据
+void init_test_data(struct test_iovec *test_vec) {
+    for (int i = 0; i < NUM_IOV; i++) {
+        // 填充每个小块数据
+        snprintf(test_vec->data[i], SMALL_DATA_SIZE, "Block_%04d:abcdefghijklmnopqrstuvwxyz", i);
+        test_vec->iov[i].iov_base = test_vec->data[i];
+        test_vec->iov[i].iov_len = strlen(test_vec->data[i]);
+    }
+}
+
+// 性能测试函数
+double test_pwritev_performance(int fd, struct test_iovec *test_vec, int iterations) {
+    struct timespec start, end;
+
+    clock_gettime(CLOCK_MONOTONIC, &start);
+
+    for (int i = 0; i < iterations; i++) {
+        ssize_t written = pwritev(fd, test_vec->iov, NUM_IOV, 0);
+        if (written == -1) {
+            perror("pwritev failed");
+            exit(EXIT_FAILURE);
+        }
+
+        // 计算总写入字节数
+        size_t total_bytes = 0;
+        for (int j = 0; j < NUM_IOV; j++) {
+            total_bytes += test_vec->iov[j].iov_len;
+        }
+
+        if (written != total_bytes) {
+            fprintf(stderr, "Partial write: expected %zu, got %zd\n", total_bytes, written);
+            exit(EXIT_FAILURE);
+        }
+    }
+
+    clock_gettime(CLOCK_MONOTONIC, &end);
+
+    double elapsed = (end.tv_sec - start.tv_sec) +
+                    (end.tv_nsec - start.tv_nsec) / 1e9;
+
+    return elapsed;
+}
+
+// 对比测试：使用单独的 write 调用
+double test_individual_writes_performance(int fd, struct test_iovec *test_vec, int iterations) {
+    struct timespec start, end;
+
+    clock_gettime(CLOCK_MONOTONIC, &start);
+
+    for (int i = 0; i < iterations; i++) {
+        off_t offset = 0;
+        for (int j = 0; j < NUM_IOV; j++) {
+            ssize_t written = pwrite(fd, test_vec->iov[j].iov_base,
+                                   test_vec->iov[j].iov_len, offset);
+            if (written == -1) {
+                perror("pwrite failed");
+                exit(EXIT_FAILURE);
+            }
+            if (written != test_vec->iov[j].iov_len) {
+                fprintf(stderr, "Partial write in individual test\n");
+                exit(EXIT_FAILURE);
+            }
+            offset += written;
+        }
+    }
+
+    clock_gettime(CLOCK_MONOTONIC, &end);
+
+    double elapsed = (end.tv_sec - start.tv_sec) +
+                    (end.tv_nsec - start.tv_nsec) / 1e9;
+
+    return elapsed;
+}
+
+
+int main(void) {
+    struct test_iovec test_vec;
+
+    printf("=== pwritev Performance Test ===\n");
+    printf("IOV count: %d\n", NUM_IOV);
+    printf("Small data size: %d bytes\n", SMALL_DATA_SIZE);
+    printf("Iterations: %d\n", TOTAL_ITERATIONS);
+    printf("\n");
+
+    // 初始化测试数据
+    init_test_data(&test_vec);
+
+    // 计算总数据大小
+    size_t total_data_size = 0;
+    for (int i = 0; i < NUM_IOV; i++) {
+        total_data_size += test_vec.iov[i].iov_len;
+    }
+    printf("Total data per pwritev call: %zu bytes\n", total_data_size);
+    printf("Total data to write: %zu KB\n",
+           (total_data_size * TOTAL_ITERATIONS) / 1024);
+    printf("\n");
+
+    // 创建测试文件
+    int fd = open(TEST_FILE, O_CREAT | O_WRONLY | O_TRUNC, 0644);
+    if (fd == -1) {
+        perror("Failed to create test file");
+        exit(EXIT_FAILURE);
+    }
+
+    // 性能测试：pwritev
+    printf("Testing pwritev performance...\n");
+    double pwritev_time = test_pwritev_performance(fd, &test_vec, TOTAL_ITERATIONS);
+    printf("pwritev total time: %.4f seconds\n", pwritev_time);
+    printf("pwritev average time per call: %.6f ms\n",
+           (pwritev_time * 1000) / TOTAL_ITERATIONS);
+    printf("pwritev throughput: %.2f MB/s\n",
+           (total_data_size * TOTAL_ITERATIONS) / (pwritev_time * 1024 * 1024));
+    printf("\n");
+
+    // 重置文件位置
+    if (ftruncate(fd, 0) == -1) {
+        perror("Failed to truncate file");
+        close(fd);
+        exit(EXIT_FAILURE);
+    }
+
+    // 性能测试：单独的 write 调用对比
+    printf("Testing individual pwrite performance (baseline)...\n");
+    double individual_time = test_individual_writes_performance(fd, &test_vec, TOTAL_ITERATIONS);
+    printf("Individual pwrite total time: %.4f seconds\n", individual_time);
+    printf("Individual pwrite average time per call: %.6f ms\n",
+           (individual_time * 1000) / TOTAL_ITERATIONS);
+    printf("Individual pwrite throughput: %.2f MB/s\n",
+           (total_data_size * TOTAL_ITERATIONS) / (individual_time * 1024 * 1024));
+    printf("\n");
+
+    // 性能对比
+    double speedup = individual_time / pwritev_time;
+    printf("Performance comparison:\n");
+    printf("pwritev is %.2fx faster than individual writes\n", speedup);
+    printf("pwritev saves %.2f%% time\n", (1 - pwritev_time / individual_time) * 100);
+    printf("\n");
+
+    // 清理
+    close(fd);
+    if (unlink(TEST_FILE) == -1) {
+        perror("Failed to remove test file");
+    }
+
+    printf("test_pwritev_perf ok\n");
+    return 0;
+}