LXR linux/tools/testing/selftests/timers/nsleep-lat.c

   1/* Measure nanosleep timer latency
   2 *              by: john stultz (john.stultz@linaro.org)
   3 *              (C) Copyright Linaro 2013
   4 *              Licensed under the GPLv2
   5 *
   6 *  To build:
   7 *      $ gcc nsleep-lat.c -o nsleep-lat -lrt
   8 *
   9 *   This program is free software: you can redistribute it and/or modify
  10 *   it under the terms of the GNU General Public License as published by
  11 *   the Free Software Foundation, either version 2 of the License, or
  12 *   (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 of
  16 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 *   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 1000000000ULL
  30
  31#define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
  32
  33
  34#define CLOCK_REALTIME                  0
  35#define CLOCK_MONOTONIC                 1
  36#define CLOCK_PROCESS_CPUTIME_ID        2
  37#define CLOCK_THREAD_CPUTIME_ID         3
  38#define CLOCK_MONOTONIC_RAW             4
  39#define CLOCK_REALTIME_COARSE           5
  40#define CLOCK_MONOTONIC_COARSE          6
  41#define CLOCK_BOOTTIME                  7
  42#define CLOCK_REALTIME_ALARM            8
  43#define CLOCK_BOOTTIME_ALARM            9
  44#define CLOCK_HWSPECIFIC                10
  45#define CLOCK_TAI                       11
  46#define NR_CLOCKIDS                     12
  47
  48#define UNSUPPORTED 0xf00f
  49
  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                printf("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                printf("Large abs latency: %lld ns :", latency/count);
 136                return -1;
 137        }
 138
 139        return 0;
 140}
 141
 142
 143
 144int main(int argc, char **argv)
 145{
 146        long long length;
 147        int clockid, ret;
 148
 149        for (clockid = CLOCK_REALTIME; clockid < NR_CLOCKIDS; clockid++) {
 150
 151                /* Skip cputime clockids since nanosleep won't increment cputime */
 152                if (clockid == CLOCK_PROCESS_CPUTIME_ID ||
 153                                clockid == CLOCK_THREAD_CPUTIME_ID ||
 154                                clockid == CLOCK_HWSPECIFIC)
 155                        continue;
 156
 157                printf("nsleep latency %-26s ", clockstring(clockid));
 158
 159                length = 10;
 160                while (length <= (NSEC_PER_SEC * 10)) {
 161                        ret = nanosleep_lat_test(clockid, length);
 162                        if (ret)
 163                                break;
 164                        length *= 100;
 165
 166                }
 167
 168                if (ret == UNSUPPORTED) {
 169                        printf("[UNSUPPORTED]\n");
 170                        continue;
 171                }
 172                if (ret < 0) {
 173                        printf("[FAILED]\n");
 174                        return ksft_exit_fail();
 175                }
 176                printf("[OK]\n");
 177        }
 178        return ksft_exit_pass();
 179}
 180