1 /* Measure nanosleep timer latency
2 * by: john stultz (john.stultz@linaro.org)
3 * (C) Copyright Linaro 2013
4 * Licensed under the GPLv2
7 * $ gcc nsleep-lat.c -o nsleep-lat -lrt
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.
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.
24 #include <sys/timex.h>
28 #include "../kselftest.h"
30 static inline int ksft_exit_pass(void)
34 static inline int ksft_exit_fail(void)
40 #define NSEC_PER_SEC 1000000000ULL
42 #define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
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
57 #define NR_CLOCKIDS 12
59 #define UNSUPPORTED 0xf00f
61 char *clockstring(int clockid)
65 return "CLOCK_REALTIME";
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";
79 return "CLOCK_BOOTTIME";
80 case CLOCK_REALTIME_ALARM:
81 return "CLOCK_REALTIME_ALARM";
82 case CLOCK_BOOTTIME_ALARM:
83 return "CLOCK_BOOTTIME_ALARM";
87 return "UNKNOWN_CLOCKID";
90 struct timespec timespec_add(struct timespec ts, unsigned long long ns)
93 while (ts.tv_nsec >= NSEC_PER_SEC) {
94 ts.tv_nsec -= NSEC_PER_SEC;
101 long long timespec_sub(struct timespec a, struct timespec b)
103 long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
105 ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
109 int nanosleep_lat_test(int clockid, long long ns)
111 struct timespec start, end, target;
112 long long latency = 0;
115 target.tv_sec = ns/NSEC_PER_SEC;
116 target.tv_nsec = ns%NSEC_PER_SEC;
118 if (clock_gettime(clockid, &start))
120 if (clock_nanosleep(clockid, 0, &target, NULL))
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);
131 if (((timespec_sub(start, end)/count)-ns) > UNRESONABLE_LATENCY) {
132 printf("Large rel latency: %lld ns :", (timespec_sub(start, end)/count)-ns);
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);
145 if (latency/count > UNRESONABLE_LATENCY) {
146 printf("Large abs latency: %lld ns :", latency/count);
155 int main(int argc, char **argv)
160 for (clockid = CLOCK_REALTIME; clockid < NR_CLOCKIDS; clockid++) {
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)
168 printf("nsleep latency %-26s ", clockstring(clockid));
171 while (length <= (NSEC_PER_SEC * 10)) {
172 ret = nanosleep_lat_test(clockid, length);
179 if (ret == UNSUPPORTED) {
180 printf("[UNSUPPORTED]\n");
184 printf("[FAILED]\n");
185 return ksft_exit_fail();
189 return ksft_exit_pass();