179 lines · c
1/* Measure nanosleep timer latency2 * by: john stultz (john.stultz@linaro.org)3 * (C) Copyright Linaro 20134 * Licensed under the GPLv25 *6 * To build:7 * $ gcc nsleep-lat.c -o nsleep-lat -lrt8 *9 * This program is free software: you can redistribute it and/or modify10 * it under the terms of the GNU General Public License as published by11 * the Free Software Foundation, either version 2 of the License, or12 * (at your option) any later version.13 *14 * This program is distributed in the hope that it will be useful,15 * but WITHOUT ANY WARRANTY; without even the implied warranty of16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the17 * GNU General Public License for more details.18 */19 20#include <stdio.h>21#include <stdlib.h>22#include <time.h>23#include <sys/time.h>24#include <sys/timex.h>25#include <string.h>26#include <signal.h>27#include "../kselftest.h"28 29#define NSEC_PER_SEC 1000000000ULL30 31#define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */32 33 34#define CLOCK_REALTIME 035#define CLOCK_MONOTONIC 136#define CLOCK_PROCESS_CPUTIME_ID 237#define CLOCK_THREAD_CPUTIME_ID 338#define CLOCK_MONOTONIC_RAW 439#define CLOCK_REALTIME_COARSE 540#define CLOCK_MONOTONIC_COARSE 641#define CLOCK_BOOTTIME 742#define CLOCK_REALTIME_ALARM 843#define CLOCK_BOOTTIME_ALARM 944#define CLOCK_HWSPECIFIC 1045#define CLOCK_TAI 1146#define NR_CLOCKIDS 1247 48#define UNSUPPORTED 0xf00f49 50char *clockstring(int clockid)51{52 switch (clockid) {53 case CLOCK_REALTIME:54 return "CLOCK_REALTIME";55 case CLOCK_MONOTONIC:56 return "CLOCK_MONOTONIC";57 case CLOCK_PROCESS_CPUTIME_ID:58 return "CLOCK_PROCESS_CPUTIME_ID";59 case CLOCK_THREAD_CPUTIME_ID:60 return "CLOCK_THREAD_CPUTIME_ID";61 case CLOCK_MONOTONIC_RAW:62 return "CLOCK_MONOTONIC_RAW";63 case CLOCK_REALTIME_COARSE:64 return "CLOCK_REALTIME_COARSE";65 case CLOCK_MONOTONIC_COARSE:66 return "CLOCK_MONOTONIC_COARSE";67 case CLOCK_BOOTTIME:68 return "CLOCK_BOOTTIME";69 case CLOCK_REALTIME_ALARM:70 return "CLOCK_REALTIME_ALARM";71 case CLOCK_BOOTTIME_ALARM:72 return "CLOCK_BOOTTIME_ALARM";73 case CLOCK_TAI:74 return "CLOCK_TAI";75 };76 return "UNKNOWN_CLOCKID";77}78 79struct timespec timespec_add(struct timespec ts, unsigned long long ns)80{81 ts.tv_nsec += ns;82 while (ts.tv_nsec >= NSEC_PER_SEC) {83 ts.tv_nsec -= NSEC_PER_SEC;84 ts.tv_sec++;85 }86 return ts;87}88 89 90long long timespec_sub(struct timespec a, struct timespec b)91{92 long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;93 94 ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;95 return ret;96}97 98int nanosleep_lat_test(int clockid, long long ns)99{100 struct timespec start, end, target;101 long long latency = 0;102 int i, count;103 104 target.tv_sec = ns/NSEC_PER_SEC;105 target.tv_nsec = ns%NSEC_PER_SEC;106 107 if (clock_gettime(clockid, &start))108 return UNSUPPORTED;109 if (clock_nanosleep(clockid, 0, &target, NULL))110 return UNSUPPORTED;111 112 count = 10;113 114 /* First check relative latency */115 clock_gettime(clockid, &start);116 for (i = 0; i < count; i++)117 clock_nanosleep(clockid, 0, &target, NULL);118 clock_gettime(clockid, &end);119 120 if (((timespec_sub(start, end)/count)-ns) > UNRESONABLE_LATENCY) {121 ksft_print_msg("Large rel latency: %lld ns :", (timespec_sub(start, end)/count)-ns);122 return -1;123 }124 125 /* Next check absolute latency */126 for (i = 0; i < count; i++) {127 clock_gettime(clockid, &start);128 target = timespec_add(start, ns);129 clock_nanosleep(clockid, TIMER_ABSTIME, &target, NULL);130 clock_gettime(clockid, &end);131 latency += timespec_sub(target, end);132 }133 134 if (latency/count > UNRESONABLE_LATENCY) {135 ksft_print_msg("Large abs latency: %lld ns :", latency/count);136 return -1;137 }138 139 return 0;140}141 142#define SKIPPED_CLOCK_COUNT 3143 144int main(int argc, char **argv)145{146 long long length;147 int clockid, ret;148 149 ksft_print_header();150 ksft_set_plan(NR_CLOCKIDS - CLOCK_REALTIME - SKIPPED_CLOCK_COUNT);151 152 for (clockid = CLOCK_REALTIME; clockid < NR_CLOCKIDS; clockid++) {153 154 /* Skip cputime clockids since nanosleep won't increment cputime */155 if (clockid == CLOCK_PROCESS_CPUTIME_ID ||156 clockid == CLOCK_THREAD_CPUTIME_ID ||157 clockid == CLOCK_HWSPECIFIC)158 continue;159 160 length = 10;161 while (length <= (NSEC_PER_SEC * 10)) {162 ret = nanosleep_lat_test(clockid, length);163 if (ret)164 break;165 length *= 100;166 167 }168 169 if (ret == UNSUPPORTED) {170 ksft_test_result_skip("%s\n", clockstring(clockid));171 } else {172 ksft_test_result(ret >= 0, "%s\n",173 clockstring(clockid));174 }175 }176 177 ksft_finished();178}179