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(a: start, b: end)/count)-ns) > UNRESONABLE_LATENCY) {
121 ksft_print_msg(msg: "Large rel latency: %lld ns :", (timespec_sub(a: start, b: 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(a: target, b: end);
132 }
133
134 if (latency/count > UNRESONABLE_LATENCY) {
135 ksft_print_msg(msg: "Large abs latency: %lld ns :", latency/count);
136 return -1;
137 }
138
139 return 0;
140}
141
142#define SKIPPED_CLOCK_COUNT 3
143
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, ns: length);
163 if (ret)
164 break;
165 length *= 100;
166
167 }
168
169 if (ret == UNSUPPORTED) {
170 ksft_test_result_skip(msg: "%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

source code of linux/tools/testing/selftests/timers/nsleep-lat.c