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Linux/tools/testing/selftests/timers/nsleep-lat.c

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  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 #ifdef KTEST
 28 #include "../kselftest.h"
 29 #else
 30 static inline int ksft_exit_pass(void)
 31 {
 32         exit(0);
 33 }
 34 static inline int ksft_exit_fail(void)
 35 {
 36         exit(1);
 37 }
 38 #endif
 39 
 40 #define NSEC_PER_SEC 1000000000ULL
 41 
 42 #define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
 43 
 44 
 45 #define CLOCK_REALTIME                  0
 46 #define CLOCK_MONOTONIC                 1
 47 #define CLOCK_PROCESS_CPUTIME_ID        2
 48 #define CLOCK_THREAD_CPUTIME_ID         3
 49 #define CLOCK_MONOTONIC_RAW             4
 50 #define CLOCK_REALTIME_COARSE           5
 51 #define CLOCK_MONOTONIC_COARSE          6
 52 #define CLOCK_BOOTTIME                  7
 53 #define CLOCK_REALTIME_ALARM            8
 54 #define CLOCK_BOOTTIME_ALARM            9
 55 #define CLOCK_HWSPECIFIC                10
 56 #define CLOCK_TAI                       11
 57 #define NR_CLOCKIDS                     12
 58 
 59 #define UNSUPPORTED 0xf00f
 60 
 61 char *clockstring(int clockid)
 62 {
 63         switch (clockid) {
 64         case CLOCK_REALTIME:
 65                 return "CLOCK_REALTIME";
 66         case CLOCK_MONOTONIC:
 67                 return "CLOCK_MONOTONIC";
 68         case CLOCK_PROCESS_CPUTIME_ID:
 69                 return "CLOCK_PROCESS_CPUTIME_ID";
 70         case CLOCK_THREAD_CPUTIME_ID:
 71                 return "CLOCK_THREAD_CPUTIME_ID";
 72         case CLOCK_MONOTONIC_RAW:
 73                 return "CLOCK_MONOTONIC_RAW";
 74         case CLOCK_REALTIME_COARSE:
 75                 return "CLOCK_REALTIME_COARSE";
 76         case CLOCK_MONOTONIC_COARSE:
 77                 return "CLOCK_MONOTONIC_COARSE";
 78         case CLOCK_BOOTTIME:
 79                 return "CLOCK_BOOTTIME";
 80         case CLOCK_REALTIME_ALARM:
 81                 return "CLOCK_REALTIME_ALARM";
 82         case CLOCK_BOOTTIME_ALARM:
 83                 return "CLOCK_BOOTTIME_ALARM";
 84         case CLOCK_TAI:
 85                 return "CLOCK_TAI";
 86         };
 87         return "UNKNOWN_CLOCKID";
 88 }
 89 
 90 struct timespec timespec_add(struct timespec ts, unsigned long long ns)
 91 {
 92         ts.tv_nsec += ns;
 93         while (ts.tv_nsec >= NSEC_PER_SEC) {
 94                 ts.tv_nsec -= NSEC_PER_SEC;
 95                 ts.tv_sec++;
 96         }
 97         return ts;
 98 }
 99 
100 
101 long long timespec_sub(struct timespec a, struct timespec b)
102 {
103         long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
104 
105         ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
106         return ret;
107 }
108 
109 int nanosleep_lat_test(int clockid, long long ns)
110 {
111         struct timespec start, end, target;
112         long long latency = 0;
113         int i, count;
114 
115         target.tv_sec = ns/NSEC_PER_SEC;
116         target.tv_nsec = ns%NSEC_PER_SEC;
117 
118         if (clock_gettime(clockid, &start))
119                 return UNSUPPORTED;
120         if (clock_nanosleep(clockid, 0, &target, NULL))
121                 return UNSUPPORTED;
122 
123         count = 10;
124 
125         /* First check relative latency */
126         clock_gettime(clockid, &start);
127         for (i = 0; i < count; i++)
128                 clock_nanosleep(clockid, 0, &target, NULL);
129         clock_gettime(clockid, &end);
130 
131         if (((timespec_sub(start, end)/count)-ns) > UNRESONABLE_LATENCY) {
132                 printf("Large rel latency: %lld ns :", (timespec_sub(start, end)/count)-ns);
133                 return -1;
134         }
135 
136         /* Next check absolute latency */
137         for (i = 0; i < count; i++) {
138                 clock_gettime(clockid, &start);
139                 target = timespec_add(start, ns);
140                 clock_nanosleep(clockid, TIMER_ABSTIME, &target, NULL);
141                 clock_gettime(clockid, &end);
142                 latency += timespec_sub(target, end);
143         }
144 
145         if (latency/count > UNRESONABLE_LATENCY) {
146                 printf("Large abs latency: %lld ns :", latency/count);
147                 return -1;
148         }
149 
150         return 0;
151 }
152 
153 
154 
155 int main(int argc, char **argv)
156 {
157         long long length;
158         int clockid, ret;
159 
160         for (clockid = CLOCK_REALTIME; clockid < NR_CLOCKIDS; clockid++) {
161 
162                 /* Skip cputime clockids since nanosleep won't increment cputime */
163                 if (clockid == CLOCK_PROCESS_CPUTIME_ID ||
164                                 clockid == CLOCK_THREAD_CPUTIME_ID ||
165                                 clockid == CLOCK_HWSPECIFIC)
166                         continue;
167 
168                 printf("nsleep latency %-26s ", clockstring(clockid));
169 
170                 length = 10;
171                 while (length <= (NSEC_PER_SEC * 10)) {
172                         ret = nanosleep_lat_test(clockid, length);
173                         if (ret)
174                                 break;
175                         length *= 100;
176 
177                 }
178 
179                 if (ret == UNSUPPORTED) {
180                         printf("[UNSUPPORTED]\n");
181                         continue;
182                 }
183                 if (ret < 0) {
184                         printf("[FAILED]\n");
185                         return ksft_exit_fail();
186                 }
187                 printf("[OK]\n");
188         }
189         return ksft_exit_pass();
190 }
191 

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