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Commit 51f91cbd authored by John Stultz's avatar John Stultz Committed by Shuah Khan
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selftests/timers: Add clock skew estimation test from timetest suite 



This adds my clock skew estimation test from the timetest suite.
It measures the drift between CLOCK_MONOTONIC and CLOCK_MONOTONIC_RAW
and compares it with the current frequency value from adjtimex.

It sometimes can trigger false failures when ntpd isn't in a
steady state, but its a useful too when doing adjtimex testing.

Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
Tested-by: default avatarPrarit Bhargava <prarit@redhat.com>
Signed-off-by: default avatarShuah Khan <shuahkh@osg.samsung.com>
parent c5fffcb2

tools/testing/selftests/timers/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -2,7 +2,7 @@ CC = $(CROSS_COMPILE)gcc 
BUILD_FLAGS = -DKTEST

CFLAGS += -O3 -Wl,-no-as-needed -Wall $(BUILD_FLAGS)

LDFLAGS += -lrt -lpthread

bins = posix_timers nanosleep inconsistency-check nsleep-lat

bins = posix_timers nanosleep inconsistency-check nsleep-lat raw_skew



all: ${bins}
@@ -11,5 +11,6 @@ run_tests: all 
	./nanosleep

	./nsleep-lat

	./inconsistency-check

	./raw_skew

clean:

	rm -f ${bins}

tools/testing/selftests/timers/raw_skew.c

0 → 100644
+154 −0
Original line number Diff line number Diff line 
/* CLOCK_MONOTONIC vs CLOCK_MONOTONIC_RAW skew test

 *		by: john stultz (johnstul@us.ibm.com)

 *		    John Stultz <john.stultz@linaro.org>

 *		(C) Copyright IBM 2012

 *		(C) Copyright Linaro Limited 2015

 *		Licensed under the GPLv2

 *

 *  To build:

 *	$ gcc raw_skew.c -o raw_skew -lrt

 *

 *   This program is free software: you can redistribute it and/or modify

 *   it under the terms of the GNU General Public License as published by

 *   the Free Software Foundation, either version 2 of the License, or

 *   (at your option) any later version.

 *

 *   This program is distributed in the hope that it will be useful,

 *   but WITHOUT ANY WARRANTY; without even the implied warranty of

 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *   GNU General Public License for more details.

 */



#include <stdio.h>

#include <unistd.h>

#include <stdlib.h>

#include <sys/time.h>

#include <sys/timex.h>

#include <time.h>

#ifdef KTEST

#include "../kselftest.h"

#else

static inline int ksft_exit_pass(void)

{

	exit(0);

}

static inline int ksft_exit_fail(void)

{

	exit(1);

}

#endif





#define CLOCK_MONOTONIC_RAW		4

#define NSEC_PER_SEC 1000000000LL



#define shift_right(x, s) ({		\

	__typeof__(x) __x = (x);	\

	__typeof__(s) __s = (s);	\

	__x < 0 ? -(-__x >> __s) : __x >> __s; \

})



long long llabs(long long val)

{

	if (val < 0)

		val = -val;

	return val;

}



unsigned long long ts_to_nsec(struct timespec ts)

{

	return ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;

}



struct timespec nsec_to_ts(long long ns)

{

	struct timespec ts;



	ts.tv_sec = ns/NSEC_PER_SEC;

	ts.tv_nsec = ns%NSEC_PER_SEC;

	return ts;

}



long long diff_timespec(struct timespec start, struct timespec end)

{

	long long start_ns, end_ns;



	start_ns = ts_to_nsec(start);

	end_ns = ts_to_nsec(end);

	return end_ns - start_ns;

}



void get_monotonic_and_raw(struct timespec *mon, struct timespec *raw)

{

	struct timespec start, mid, end;

	long long diff = 0, tmp;

	int i;



	for (i = 0; i < 3; i++) {

		long long newdiff;



		clock_gettime(CLOCK_MONOTONIC, &start);

		clock_gettime(CLOCK_MONOTONIC_RAW, &mid);

		clock_gettime(CLOCK_MONOTONIC, &end);



		newdiff = diff_timespec(start, end);

		if (diff == 0 || newdiff < diff) {

			diff = newdiff;

			*raw = mid;

			tmp = (ts_to_nsec(start) + ts_to_nsec(end))/2;

			*mon = nsec_to_ts(tmp);

		}

	}

}



int main(int argv, char **argc)

{

	struct timespec mon, raw, start, end;

	long long delta1, delta2, interval, eppm, ppm;

	struct timex tx1, tx2;



	setbuf(stdout, NULL);



	if (clock_gettime(CLOCK_MONOTONIC_RAW, &raw)) {

		printf("ERR: NO CLOCK_MONOTONIC_RAW\n");

		return -1;

	}



	tx1.modes = 0;

	adjtimex(&tx1);

	get_monotonic_and_raw(&mon, &raw);

	start = mon;

	delta1 = diff_timespec(mon, raw);



	if (tx1.offset)

		printf("WARNING: ADJ_OFFSET in progress, this will cause inaccurate results\n");



	printf("Estimating clock drift: ");

	sleep(120);



	get_monotonic_and_raw(&mon, &raw);

	end = mon;

	tx2.modes = 0;

	adjtimex(&tx2);

	delta2 = diff_timespec(mon, raw);



	interval = diff_timespec(start, end);



	/* calculate measured ppm between MONOTONIC and MONOTONIC_RAW */

	eppm = ((delta2-delta1)*NSEC_PER_SEC)/interval;

	eppm = -eppm;

	printf("%lld.%i(est)", eppm/1000, abs((int)(eppm%1000)));



	/* Avg the two actual freq samples adjtimex gave us */

	ppm = (tx1.freq + tx2.freq) * 1000 / 2;

	ppm = (long long)tx1.freq * 1000;

	ppm = shift_right(ppm, 16);

	printf(" %lld.%i(act)", ppm/1000, abs((int)(ppm%1000)));



	if (llabs(eppm - ppm) > 1000) {

		printf("	[FAILED]\n");

		return ksft_exit_fail();

	}

	printf("	[OK]\n");

	return  ksft_exit_pass();

}