It's time to stop!

timeperf.c

#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;
}