/* Measure nanosleep timer latency * by: john stultz (john.stultz@linaro.org) * (C) Copyright Linaro 2013 * Licensed under the GPLv2 * * To build: * $ gcc nsleep-lat.c -o nsleep-lat -lrt * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. */ #include <stdio.h> #include <stdlib.h> #include <time.h> #include <sys/time.h> #include <sys/timex.h> #include <string.h> #include <signal.h> #ifdef KTEST #include "../kselftest.h" #else static inline int ksft_exit_pass(void) { exit(0); } static inline int ksft_exit_fail(void) { exit(1); } #endif #define NSEC_PER_SEC 1000000000ULL #define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */ #define CLOCK_REALTIME 0 #define CLOCK_MONOTONIC 1 #define CLOCK_PROCESS_CPUTIME_ID 2 #define CLOCK_THREAD_CPUTIME_ID 3 #define CLOCK_MONOTONIC_RAW 4 #define CLOCK_REALTIME_COARSE 5 #define CLOCK_MONOTONIC_COARSE 6 #define CLOCK_BOOTTIME 7 #define CLOCK_REALTIME_ALARM 8 #define CLOCK_BOOTTIME_ALARM 9 #define CLOCK_HWSPECIFIC 10 #define CLOCK_TAI 11 #define NR_CLOCKIDS 12 #define UNSUPPORTED 0xf00f char *clockstring(int clockid) { switch (clockid) { case CLOCK_REALTIME: return "CLOCK_REALTIME"; case CLOCK_MONOTONIC: return "CLOCK_MONOTONIC"; case CLOCK_PROCESS_CPUTIME_ID: return "CLOCK_PROCESS_CPUTIME_ID"; case CLOCK_THREAD_CPUTIME_ID: return "CLOCK_THREAD_CPUTIME_ID"; case CLOCK_MONOTONIC_RAW: return "CLOCK_MONOTONIC_RAW"; case CLOCK_REALTIME_COARSE: return "CLOCK_REALTIME_COARSE"; case CLOCK_MONOTONIC_COARSE: return "CLOCK_MONOTONIC_COARSE"; case CLOCK_BOOTTIME: return "CLOCK_BOOTTIME"; case CLOCK_REALTIME_ALARM: return "CLOCK_REALTIME_ALARM"; case CLOCK_BOOTTIME_ALARM: return "CLOCK_BOOTTIME_ALARM"; case CLOCK_TAI: return "CLOCK_TAI"; }; return "UNKNOWN_CLOCKID"; } struct timespec timespec_add(struct timespec ts, unsigned long long ns) { ts.tv_nsec += ns; while (ts.tv_nsec >= NSEC_PER_SEC) { ts.tv_nsec -= NSEC_PER_SEC; ts.tv_sec++; } return ts; } long long timespec_sub(struct timespec a, struct timespec b) { long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec; ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec; return ret; } int nanosleep_lat_test(int clockid, long long ns) { struct timespec start, end, target; long long latency = 0; int i, count; target.tv_sec = ns/NSEC_PER_SEC; target.tv_nsec = ns%NSEC_PER_SEC; if (clock_gettime(clockid, &start)) return UNSUPPORTED; if (clock_nanosleep(clockid, 0, &target, NULL)) return UNSUPPORTED; count = 10; /* First check relative latency */ clock_gettime(clockid, &start); for (i = 0; i < count; i++) clock_nanosleep(clockid, 0, &target, NULL); clock_gettime(clockid, &end); if (((timespec_sub(start, end)/count)-ns) > UNRESONABLE_LATENCY) { printf("Large rel latency: %lld ns :", (timespec_sub(start, end)/count)-ns); return -1; } /* Next check absolute latency */ for (i = 0; i < count; i++) { clock_gettime(clockid, &start); target = timespec_add(start, ns); clock_nanosleep(clockid, TIMER_ABSTIME, &target, NULL); clock_gettime(clockid, &end); latency += timespec_sub(target, end); } if (latency/count > UNRESONABLE_LATENCY) { printf("Large abs latency: %lld ns :", latency/count); return -1; } return 0; } int main(int argc, char **argv) { long long length; int clockid, ret; for (clockid = CLOCK_REALTIME; clockid < NR_CLOCKIDS; clockid++) { /* Skip cputime clockids since nanosleep won't increment cputime */ if (clockid == CLOCK_PROCESS_CPUTIME_ID || clockid == CLOCK_THREAD_CPUTIME_ID || clockid == CLOCK_HWSPECIFIC) continue; printf("nsleep latency %-26s ", clockstring(clockid)); length = 10; while (length <= (NSEC_PER_SEC * 10)) { ret = nanosleep_lat_test(clockid, length); if (ret) break; length *= 100; } if (ret == UNSUPPORTED) { printf("[UNSUPPORTED]\n"); continue; } if (ret < 0) { printf("[FAILED]\n"); return ksft_exit_fail(); } printf("[OK]\n"); } return ksft_exit_pass(); }