Created
October 12, 2022 05:35
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| #include <asm/unistd.h> | |
| #include <inttypes.h> | |
| #include <linux/perf_event.h> | |
| #include <stdio.h> | |
| #include <sys/mman.h> | |
| #include <unistd.h> | |
| #include <stdint.h> | |
| static uint64_t mul_u64_u32_shr(uint64_t cyc, uint32_t mult, uint32_t shift) { | |
| __uint128_t x = cyc; | |
| x *= mult; | |
| x >>= shift; | |
| return x; | |
| } | |
| static long perf_event_open(struct perf_event_attr *hw_event, pid_t pid, | |
| int cpu, int group_fd, unsigned long flags) { | |
| return syscall(__NR_perf_event_open, hw_event, pid, cpu, group_fd, flags); | |
| } | |
| static double get_rdtsc_ms() { | |
| struct perf_event_attr pe = { | |
| .type = PERF_TYPE_HARDWARE, | |
| .size = sizeof(struct perf_event_attr), | |
| .config = PERF_COUNT_HW_INSTRUCTIONS, | |
| .disabled = 1, | |
| .exclude_kernel = 1, | |
| .exclude_hv = 1 | |
| }; | |
| int fd = perf_event_open(&pe, 0, -1, -1, 0); | |
| if (fd == -1) { | |
| perror("perf_event_open failed"); | |
| return 1; | |
| } | |
| void *addr = mmap(NULL, 4*1024, PROT_READ, MAP_SHARED, fd, 0); | |
| if (!addr) { | |
| perror("mmap failed"); | |
| return 1; | |
| } | |
| struct perf_event_mmap_page *pc = addr; | |
| if (pc->cap_user_time != 1) { | |
| fprintf(stderr, "Perf system doesn't support user time\n"); | |
| return 1; | |
| } | |
| double nanos = (double)mul_u64_u32_shr(1000000, pc->time_mult, pc->time_shift); | |
| return nanos / 1000000000; | |
| } |
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