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
30static inline int ksft_exit_pass(void)
31{
32	exit(0);
33}
34static 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
61char *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
90struct 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
101long 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
109int 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
155int 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