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 <include/vdso/time64.h>
 28#include "kselftest.h"
 29
 30#define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
 31
 32/* CLOCK_HWSPECIFIC == CLOCK_SGI_CYCLE (Deprecated) */
 33#define CLOCK_HWSPECIFIC		10
 34
 35#define UNSUPPORTED 0xf00f
 36
 37char *clockstring(int clockid)
 38{
 39	switch (clockid) {
 40	case CLOCK_REALTIME:
 41		return "CLOCK_REALTIME";
 42	case CLOCK_MONOTONIC:
 43		return "CLOCK_MONOTONIC";
 44	case CLOCK_PROCESS_CPUTIME_ID:
 45		return "CLOCK_PROCESS_CPUTIME_ID";
 46	case CLOCK_THREAD_CPUTIME_ID:
 47		return "CLOCK_THREAD_CPUTIME_ID";
 48	case CLOCK_MONOTONIC_RAW:
 49		return "CLOCK_MONOTONIC_RAW";
 50	case CLOCK_REALTIME_COARSE:
 51		return "CLOCK_REALTIME_COARSE";
 52	case CLOCK_MONOTONIC_COARSE:
 53		return "CLOCK_MONOTONIC_COARSE";
 54	case CLOCK_BOOTTIME:
 55		return "CLOCK_BOOTTIME";
 56	case CLOCK_REALTIME_ALARM:
 57		return "CLOCK_REALTIME_ALARM";
 58	case CLOCK_BOOTTIME_ALARM:
 59		return "CLOCK_BOOTTIME_ALARM";
 60	case CLOCK_TAI:
 61		return "CLOCK_TAI";
 62	};
 63	return "UNKNOWN_CLOCKID";
 64}
 65
 66struct timespec timespec_add(struct timespec ts, unsigned long long ns)
 67{
 68	ts.tv_nsec += ns;
 69	while (ts.tv_nsec >= NSEC_PER_SEC) {
 70		ts.tv_nsec -= NSEC_PER_SEC;
 71		ts.tv_sec++;
 72	}
 73	return ts;
 74}
 75
 76
 77long long timespec_sub(struct timespec a, struct timespec b)
 78{
 79	long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
 80
 81	ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
 82	return ret;
 83}
 84
 85int nanosleep_lat_test(int clockid, long long ns)
 86{
 87	struct timespec start, end, target;
 88	long long latency = 0;
 89	int i, count;
 90
 91	target.tv_sec = ns/NSEC_PER_SEC;
 92	target.tv_nsec = ns%NSEC_PER_SEC;
 93
 94	if (clock_gettime(clockid, &start))
 95		return UNSUPPORTED;
 96	if (clock_nanosleep(clockid, 0, &target, NULL))
 97		return UNSUPPORTED;
 98
 99	count = 10;
100
101	/* First check relative latency */
102	clock_gettime(clockid, &start);
103	for (i = 0; i < count; i++)
104		clock_nanosleep(clockid, 0, &target, NULL);
105	clock_gettime(clockid, &end);
106
107	if (((timespec_sub(start, end)/count)-ns) > UNRESONABLE_LATENCY) {
108		ksft_print_msg("Large rel latency: %lld ns :", (timespec_sub(start, end)/count)-ns);
109		return -1;
110	}
111
112	/* Next check absolute latency */
113	for (i = 0; i < count; i++) {
114		clock_gettime(clockid, &start);
115		target = timespec_add(start, ns);
116		clock_nanosleep(clockid, TIMER_ABSTIME, &target, NULL);
117		clock_gettime(clockid, &end);
118		latency += timespec_sub(target, end);
119	}
120
121	if (latency/count > UNRESONABLE_LATENCY) {
122		ksft_print_msg("Large abs latency: %lld ns :", latency/count);
123		return -1;
124	}
125
126	return 0;
127}
128
129#define SKIPPED_CLOCK_COUNT 3
130
131int main(int argc, char **argv)
132{
133	long long length;
134	int clockid, ret;
135	int max_clocks = CLOCK_TAI + 1;
136
137	ksft_print_header();
138	ksft_set_plan(max_clocks - CLOCK_REALTIME - SKIPPED_CLOCK_COUNT);
139
140	for (clockid = CLOCK_REALTIME; clockid < max_clocks; clockid++) {
141
142		/* Skip cputime clockids since nanosleep won't increment cputime */
143		if (clockid == CLOCK_PROCESS_CPUTIME_ID ||
144				clockid == CLOCK_THREAD_CPUTIME_ID ||
145				clockid == CLOCK_HWSPECIFIC)
146			continue;
147
148		length = 10;
149		while (length <= (NSEC_PER_SEC * 10)) {
150			ret = nanosleep_lat_test(clockid, length);
151			if (ret)
152				break;
153			length *= 100;
154
155		}
156
157		if (ret == UNSUPPORTED) {
158			ksft_test_result_skip("%s\n", clockstring(clockid));
159		} else {
160			ksft_test_result(ret >= 0, "%s\n",
161					 clockstring(clockid));
162		}
163	}
164
165	ksft_finished();
166}