selftests/powerpc: Add Anton's null_syscall benchmark to the selftests

context_switch

mmap_bench

futex_bench

null_syscall

TEST_PROGS := gettimeofday context_switch mmap_bench futex_bench

TEST_PROGS := gettimeofday context_switch mmap_bench futex_bench null_syscall

CFLAGS += -O2

/*

 * Test null syscall performance

 *

 * Copyright (C) 2009-2015 Anton Blanchard, IBM

 *

 * 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.

 */

#define NR_LOOPS 10000000

#include <string.h>

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <time.h>

#include <sys/types.h>

#include <sys/time.h>

#include <signal.h>

static volatile int soak_done;

unsigned long long clock_frequency;

unsigned long long timebase_frequency;

double timebase_multiplier;

static inline unsigned long long mftb(void)

{

	unsigned long low;

	asm volatile("mftb %0" : "=r" (low));

	return low;

}

static void sigalrm_handler(int unused)

{

	soak_done = 1;

}

/*

 * Use a timer instead of busy looping on clock_gettime() so we don't

 * pollute profiles with glibc and VDSO hits.

 */

static void cpu_soak_usecs(unsigned long usecs)

{

	struct itimerval val;

	memset(&val, 0, sizeof(val));

	val.it_value.tv_usec = usecs;

	signal(SIGALRM, sigalrm_handler);

	setitimer(ITIMER_REAL, &val, NULL);

	while (1) {

		if (soak_done)

			break;

	}

	signal(SIGALRM, SIG_DFL);

}

/*

 * This only works with recent kernels where cpufreq modifies

 * /proc/cpuinfo dynamically.

 */

static void get_proc_frequency(void)

{

	FILE *f;

	char line[128];

	char *p, *end;

	unsigned long v;

	double d;

	char *override;

	/* Try to get out of low power/low frequency mode */

	cpu_soak_usecs(0.25 * 1000000);

	f = fopen("/proc/cpuinfo", "r");

	if (f == NULL)

		return;

	timebase_frequency = 0;

	while (fgets(line, sizeof(line), f) != NULL) {

		if (strncmp(line, "timebase", 8) == 0) {

			p = strchr(line, ':');

			if (p != NULL) {

				v = strtoull(p + 1, &end, 0);

				if (end != p + 1)

					timebase_frequency = v;

			}

		}

		if (((strncmp(line, "clock", 5) == 0) ||

		     (strncmp(line, "cpu MHz", 7) == 0))) {

			p = strchr(line, ':');

			if (p != NULL) {

				d = strtod(p + 1, &end);

				if (end != p + 1) {

					/* Find fastest clock frequency */

					if ((d * 1000000ULL) > clock_frequency)

						clock_frequency = d * 1000000ULL;

				}

			}

		}

	}

	fclose(f);

	override = getenv("FREQUENCY");

	if (override)

		clock_frequency = strtoull(override, NULL, 10);

	if (timebase_frequency)

		timebase_multiplier = (double)clock_frequency

					/ timebase_frequency;

	else

		timebase_multiplier = 1;

}

static void do_null_syscall(unsigned long nr)

{

	unsigned long i;

	for (i = 0; i < nr; i++)

		getppid();

}

#define TIME(A, STR) \

int main(void)

{

	unsigned long tb_start, tb_now;

	struct timespec tv_start, tv_now;

	unsigned long long elapsed_ns, elapsed_tb;

	get_proc_frequency();

	clock_gettime(CLOCK_MONOTONIC, &tv_start);

	tb_start = mftb();

	do_null_syscall(NR_LOOPS);

	clock_gettime(CLOCK_MONOTONIC, &tv_now);

	tb_now = mftb();

	elapsed_ns = (tv_now.tv_sec - tv_start.tv_sec) * 1000000000ULL +

			(tv_now.tv_nsec - tv_start.tv_nsec);

	elapsed_tb = tb_now - tb_start;

	printf("%10.2f ns %10.2f cycles\n", (float)elapsed_ns / NR_LOOPS,

			(float)elapsed_tb * timebase_multiplier / NR_LOOPS);

	return 0;

}