101 lines
2.5 KiB
C
101 lines
2.5 KiB
C
// Compile code with gcc -o bm2 bm2.c -lrt -Wall -O2
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// Execute code with sudo ./bm2
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#include <stdio.h>
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#include <stdlib.h>
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#include <time.h>
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#include <signal.h>
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#include <sys/mman.h>
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#include <unistd.h>
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#include <sched.h>
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#include <errno.h>
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#include <string.h>
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#include <limits.h>
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#define ITERATIONS 1000
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#define NS_PER_SEC 1000000000L
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timer_t timer_id;
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volatile sig_atomic_t timer_expired = 0;
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struct timespec start, end;
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void timer_handler(int signum) {
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timer_expired = 1;
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clock_gettime(CLOCK_MONOTONIC, &end);
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}
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void configure_realtime_scheduling() {
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struct sched_param param;
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param.sched_priority = sched_get_priority_max(SCHED_FIFO);
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if (sched_setscheduler(0, SCHED_FIFO, ¶m) == -1) {
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perror("sched_setscheduler");
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exit(EXIT_FAILURE);
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}
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}
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void lock_memory() {
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if (mlockall(MCL_CURRENT | MCL_FUTURE) == -1) {
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perror("mlockall");
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exit(EXIT_FAILURE);
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}
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}
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void benchmark_timer() {
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long long total_jitter = 0;
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long long max_jitter = 0;
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long long min_jitter = LLONG_MAX;
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struct sigevent sev;
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sev.sigev_notify = SIGEV_SIGNAL;
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sev.sigev_signo = SIGRTMIN;
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sev.sigev_value.sival_ptr = &timer_id;
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if (timer_create(CLOCK_MONOTONIC, &sev, &timer_id) == -1) {
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perror("timer_create");
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exit(EXIT_FAILURE);
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}
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struct itimerspec its;
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its.it_value.tv_sec = 0;
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its.it_value.tv_nsec = 1000000; // 1 ms
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its.it_interval = its.it_value;
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signal(SIGRTMIN, timer_handler);
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if (timer_settime(timer_id, 0, &its, NULL) == -1) {
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perror("timer_settime");
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exit(EXIT_FAILURE);
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}
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clock_gettime(CLOCK_MONOTONIC, &start);
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for (int i = 0; i < ITERATIONS; i++) {
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while (!timer_expired);
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clock_gettime(CLOCK_MONOTONIC, &end);
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long long elapsed = (end.tv_sec - start.tv_sec) * NS_PER_SEC + (end.tv_nsec - start.tv_nsec);
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long long jitter = elapsed - its.it_interval.tv_nsec;
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total_jitter += llabs(jitter);
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if (jitter > max_jitter) max_jitter = jitter;
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if (jitter < min_jitter) min_jitter = jitter;
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timer_expired = 0;
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start = end;
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}
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printf("\nTimer Benchmark:\n");
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printf("Average jitter: %lld ns\n", total_jitter / ITERATIONS);
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printf("Max jitter: %lld ns\n", max_jitter);
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printf("Min jitter: %lld ns\n", min_jitter);
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timer_delete(timer_id);
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}
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int main() {
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configure_realtime_scheduling();
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lock_memory();
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benchmark_timer();
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return 0;
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}
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