selftests/powerpc: Import Anton's context_switch2 benchmark

This gets referred to a lot in commit messages, so let's pull it into
the selftests.

Almost vanilla from: http://ozlabs.org/~anton/junkcode/context_switch2.c

Signed-off-by: Anton Blanchard <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Acked-by: Anton Blanchard <[e-mail]>

tools/testing/selftests/powerpc/benchmarks/.gitignore

···
 gettimeofday
+context_switch

tools/testing/selftests/powerpc/benchmarks/Makefile

···
-TEST_PROGS := gettimeofday
+TEST_PROGS := gettimeofday context_switch
 
 CFLAGS += -O2
 
 all: $(TEST_PROGS)
 
 $(TEST_PROGS): ../harness.c
+
+context_switch: LDLIBS += -lpthread
 
 include ../../lib.mk
 

tools/testing/selftests/powerpc/benchmarks/context_switch.c

···
+/*
+ * Context switch microbenchmark.
+ *
+ * Copyright (C) 2015 Anton Blanchard <[e-mail]>, 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 _GNU_SOURCE
+#include <sched.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <getopt.h>
+#include <signal.h>
+#include <assert.h>
+#include <pthread.h>
+#include <limits.h>
+#include <sys/time.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/shm.h>
+#include <linux/futex.h>
+
+static unsigned int timeout = INT_MAX;
+
+static int touch_vdso;
+struct timeval tv;
+
+static int touch_fp;
+double fp;
+
+static int touch_vector;
+typedef int v4si __attribute__ ((vector_size (16)));
+v4si a, b, c;
+
+#ifdef __powerpc__
+static int touch_altivec;
+
+static void __attribute__((__target__("no-vsx"))) altivec_touch_fn(void)
+{
+	c = a + b;
+}
+#endif
+
+static void touch(void)
+{
+	if (touch_vdso)
+		gettimeofday(&tv, NULL);
+
+	if (touch_fp)
+		fp += 0.1;
+
+#ifdef __powerpc__
+	if (touch_altivec)
+		altivec_touch_fn();
+#endif
+
+	if (touch_vector)
+		c = a + b;
+
+	asm volatile("# %0 %1 %2": : "r"(&tv), "r"(&fp), "r"(&c));
+}
+
+static void start_thread_on(void *(*fn)(void *), void *arg, unsigned long cpu)
+{
+	pthread_t tid;
+	cpu_set_t cpuset;
+	pthread_attr_t attr;
+
+	CPU_ZERO(&cpuset);
+	CPU_SET(cpu, &cpuset);
+
+	pthread_attr_init(&attr);
+
+	if (pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpuset)) {
+		perror("pthread_attr_setaffinity_np");
+		exit(1);
+	}
+
+	if (pthread_create(&tid, &attr, fn, arg)) {
+		perror("pthread_create");
+		exit(1);
+	}
+}
+
+static void start_process_on(void *(*fn)(void *), void *arg, unsigned long cpu)
+{
+	int pid;
+	cpu_set_t cpuset;
+
+	pid = fork();
+	if (pid == -1) {
+		perror("fork");
+		exit(1);
+	}
+
+	if (pid)
+		return;
+
+	CPU_ZERO(&cpuset);
+	CPU_SET(cpu, &cpuset);
+
+	if (sched_setaffinity(0, sizeof(cpuset), &cpuset)) {
+		perror("sched_setaffinity");
+		exit(1);
+	}
+
+	fn(arg);
+
+	exit(0);
+}
+
+static unsigned long iterations;
+static unsigned long iterations_prev;
+
+static void sigalrm_handler(int junk)
+{
+	unsigned long i = iterations;
+
+	printf("%ld\n", i - iterations_prev);
+	iterations_prev = i;
+
+	if (--timeout == 0)
+		kill(0, SIGUSR1);
+
+	alarm(1);
+}
+
+static void sigusr1_handler(int junk)
+{
+	exit(0);
+}
+
+struct actions {
+	void (*setup)(int, int);
+	void *(*thread1)(void *);
+	void *(*thread2)(void *);
+};
+
+#define READ 0
+#define WRITE 1
+
+static int pipe_fd1[2];
+static int pipe_fd2[2];
+
+static void pipe_setup(int cpu1, int cpu2)
+{
+	if (pipe(pipe_fd1) || pipe(pipe_fd2))
+		exit(1);
+}
+
+static void *pipe_thread1(void *arg)
+{
+	signal(SIGALRM, sigalrm_handler);
+	alarm(1);
+
+	while (1) {
+		assert(read(pipe_fd1[READ], &c, 1) == 1);
+		touch();
+
+		assert(write(pipe_fd2[WRITE], &c, 1) == 1);
+		touch();
+
+		iterations += 2;
+	}
+
+	return NULL;
+}
+
+static void *pipe_thread2(void *arg)
+{
+	while (1) {
+		assert(write(pipe_fd1[WRITE], &c, 1) == 1);
+		touch();
+
+		assert(read(pipe_fd2[READ], &c, 1) == 1);
+		touch();
+	}
+
+	return NULL;
+}
+
+static struct actions pipe_actions = {
+	.setup = pipe_setup,
+	.thread1 = pipe_thread1,
+	.thread2 = pipe_thread2,
+};
+
+static void yield_setup(int cpu1, int cpu2)
+{
+	if (cpu1 != cpu2) {
+		fprintf(stderr, "Both threads must be on the same CPU for yield test\n");
+		exit(1);
+	}
+}
+
+static void *yield_thread1(void *arg)
+{
+	signal(SIGALRM, sigalrm_handler);
+	alarm(1);
+
+	while (1) {
+		sched_yield();
+		touch();
+
+		iterations += 2;
+	}
+
+	return NULL;
+}
+
+static void *yield_thread2(void *arg)
+{
+	while (1) {
+		sched_yield();
+		touch();
+	}
+
+	return NULL;
+}
+
+static struct actions yield_actions = {
+	.setup = yield_setup,
+	.thread1 = yield_thread1,
+	.thread2 = yield_thread2,
+};
+
+static long sys_futex(void *addr1, int op, int val1, struct timespec *timeout,
+		      void *addr2, int val3)
+{
+	return syscall(SYS_futex, addr1, op, val1, timeout, addr2, val3);
+}
+
+static unsigned long cmpxchg(unsigned long *p, unsigned long expected,
+			     unsigned long desired)
+{
+	unsigned long exp = expected;
+
+	__atomic_compare_exchange_n(p, &exp, desired, 0,
+				    __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
+	return exp;
+}
+
+static unsigned long xchg(unsigned long *p, unsigned long val)
+{
+	return __atomic_exchange_n(p, val, __ATOMIC_SEQ_CST);
+}
+
+static int mutex_lock(unsigned long *m)
+{
+	int c;
+
+	c = cmpxchg(m, 0, 1);
+	if (!c)
+		return 0;
+
+	if (c == 1)
+		c = xchg(m, 2);
+
+	while (c) {
+		sys_futex(m, FUTEX_WAIT, 2, NULL, NULL, 0);
+		c = xchg(m, 2);
+	}
+
+	return 0;
+}
+
+static int mutex_unlock(unsigned long *m)
+{
+	if (*m == 2)
+		*m = 0;
+	else if (xchg(m, 0) == 1)
+		return 0;
+
+	sys_futex(m, FUTEX_WAKE, 1, NULL, NULL, 0);
+
+	return 0;
+}
+
+static unsigned long *m1, *m2;
+
+static void futex_setup(int cpu1, int cpu2)
+{
+	int shmid;
+	void *shmaddr;
+
+	shmid = shmget(IPC_PRIVATE, getpagesize(), SHM_R | SHM_W);
+	if (shmid < 0) {
+		perror("shmget");
+		exit(1);
+	}
+
+	shmaddr = shmat(shmid, NULL, 0);
+	if (shmaddr == (char *)-1) {
+		perror("shmat");
+		shmctl(shmid, IPC_RMID, NULL);
+		exit(1);
+	}
+
+	shmctl(shmid, IPC_RMID, NULL);
+
+	m1 = shmaddr;
+	m2 = shmaddr + sizeof(*m1);
+
+	*m1 = 0;
+	*m2 = 0;
+
+	mutex_lock(m1);
+	mutex_lock(m2);
+}
+
+static void *futex_thread1(void *arg)
+{
+	signal(SIGALRM, sigalrm_handler);
+	alarm(1);
+
+	while (1) {
+		mutex_lock(m2);
+		mutex_unlock(m1);
+
+		iterations += 2;
+	}
+
+	return NULL;
+}
+
+static void *futex_thread2(void *arg)
+{
+	while (1) {
+		mutex_unlock(m2);
+		mutex_lock(m1);
+	}
+
+	return NULL;
+}
+
+static struct actions futex_actions = {
+	.setup = futex_setup,
+	.thread1 = futex_thread1,
+	.thread2 = futex_thread2,
+};
+
+static int processes;
+
+static struct option options[] = {
+	{ "test", required_argument, 0, 't' },
+	{ "process", no_argument, &processes, 1 },
+	{ "timeout", required_argument, 0, 's' },
+	{ "vdso", no_argument, &touch_vdso, 1 },
+	{ "fp", no_argument, &touch_fp, 1 },
+#ifdef __powerpc__
+	{ "altivec", no_argument, &touch_altivec, 1 },
+#endif
+	{ "vector", no_argument, &touch_vector, 1 },
+	{ 0, },
+};
+
+static void usage(void)
+{
+	fprintf(stderr, "Usage: context_switch2 <options> CPU1 CPU2\n\n");
+	fprintf(stderr, "\t\t--test=X\tpipe, futex or yield\n");
+	fprintf(stderr, "\t\t--process\tUse processes (default threads)\n");
+	fprintf(stderr, "\t\t--timeout=X\tDuration in seconds to run\n");
+	fprintf(stderr, "\t\t--vdso\t\ttouch VDSO\n");
+	fprintf(stderr, "\t\t--fp\t\ttouch FP\n");
+#ifdef __powerpc__
+	fprintf(stderr, "\t\t--altivec\ttouch altivec\n");
+#endif
+	fprintf(stderr, "\t\t--vector\ttouch vector\n");
+}
+
+int main(int argc, char *argv[])
+{
+	signed char c;
+	struct actions *actions = &pipe_actions;
+	int cpu1;
+	int cpu2;
+	static void (*start_fn)(void *(*fn)(void *), void *arg, unsigned long cpu);
+
+	while (1) {
+		int option_index = 0;
+
+		c = getopt_long(argc, argv, "", options, &option_index);
+
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 0:
+			if (options[option_index].flag != 0)
+				break;
+
+			usage();
+			exit(1);
+			break;
+
+		case 't':
+			if (!strcmp(optarg, "pipe")) {
+				actions = &pipe_actions;
+			} else if (!strcmp(optarg, "yield")) {
+				actions = &yield_actions;
+			} else if (!strcmp(optarg, "futex")) {
+				actions = &futex_actions;
+			} else {
+				usage();
+				exit(1);
+			}
+			break;
+
+		case 's':
+			timeout = atoi(optarg);
+			break;
+
+		default:
+			usage();
+			exit(1);
+		}
+	}
+
+	if (processes)
+		start_fn = start_process_on;
+	else
+		start_fn = start_thread_on;
+
+	if (((argc - optind) != 2)) {
+		usage();
+		exit(1);
+	}
+
+	/* Create a new process group so we can signal everyone for exit */
+	setpgid(getpid(), getpid());
+
+	signal(SIGUSR1, sigusr1_handler);
+
+	cpu1 = atoi(argv[optind++]);
+	cpu2 = atoi(argv[optind++]);
+
+	actions->setup(cpu1, cpu2);
+
+	start_fn(actions->thread1, NULL, cpu1);
+	start_fn(actions->thread2, NULL, cpu2);
+
+	while (1)
+		sleep(3600);
+
+	return 0;
+}