[PATCH 2/3] perf bench: port futex_wait.c of futextest to perf bench

[Hitoshi Mitake <h.mitake@gmail.com>]

This patch ports futex_wait.c of futextest[1] to perf bench, as
subsystem "futex" and its command "wait". This measures performance of
iterations of FUTEX_WAIT, unit is kilo iteration of lock and unlock
per second. Iterations, numbers of threads and futexes can be
specified with command line options: -i for iteration, -t for number
of threads, -f for number of futexes.

example of usage:
| # Running futex/wait benchmark...
| # 256 threads and 1 futexes (256 threads for 1 futex)
| 7.15s user, 60.24s system, 8.56s wall, 7.87 cores
| Result: 11682 Kiter/s

[1]: http://git.kernel.org/?p=linux/kernel/git/dvhart/futextest.git

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Darren Hart <dvhltc@us.ibm.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Hitoshi Mitake <h.mitake@gmail.com>
---
 tools/perf/Makefile           |    1 +
 tools/perf/bench/bench.h      |    1 +
 tools/perf/bench/futex-wait.c |  295 +++++++++++++++++++++++++++++++++++++++++
 tools/perf/builtin-bench.c    |   13 ++
 4 files changed, 310 insertions(+), 0 deletions(-)
 create mode 100644 tools/perf/bench/futex-wait.c

diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index cca5bb8..5c395a3 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -443,6 +443,7 @@ BUILTIN_OBJS += $(OUTPUT)bench/mem-memset-x86-64-asm.o
 endif
 BUILTIN_OBJS += $(OUTPUT)bench/mem-memcpy.o
 BUILTIN_OBJS += $(OUTPUT)bench/mem-memset.o
+BUILTIN_OBJS += $(OUTPUT)bench/futex-wait.o
 
 BUILTIN_OBJS += $(OUTPUT)builtin-diff.o
 BUILTIN_OBJS += $(OUTPUT)builtin-evlist.o
diff --git a/tools/perf/bench/bench.h b/tools/perf/bench/bench.h
index 8f89998..f188b1d 100644
--- a/tools/perf/bench/bench.h
+++ b/tools/perf/bench/bench.h
@@ -6,6 +6,7 @@ extern int bench_sched_pipe(int argc, const char **argv, const char *prefix);
 extern int bench_mem_memcpy(int argc, const char **argv,
 			    const char *prefix __maybe_unused);
 extern int bench_mem_memset(int argc, const char **argv, const char *prefix);
+extern int bench_futex_wait(int argc, const char **argv, const char *prefix);
 
 #define BENCH_FORMAT_DEFAULT_STR	"default"
 #define BENCH_FORMAT_DEFAULT		0
diff --git a/tools/perf/bench/futex-wait.c b/tools/perf/bench/futex-wait.c
new file mode 100644
index 0000000..ef21f62
--- /dev/null
+++ b/tools/perf/bench/futex-wait.c
@@ -0,0 +1,295 @@
+/*
+ * futex-wait.c
+ *
+ * Measure FUTEX_WAIT operations per second.
+ * based on futex_wait.c of futextest by Darren Hart <dvhart@linux.intel.com>
+ * and Michel Lespinasse <walken@google.com>
+ *
+ * ported to perf bench by Hitoshi Mitake <h.mitake@gmail.com>
+ *
+ * original futextest:
+ * http://git.kernel.org/?p=linux/kernel/git/dvhart/futextest.git
+ */
+
+#include "../perf.h"
+#include "../util.h"
+#include "../util/parse-options.h"
+
+#include "../../include/tools/futex.h"
+#include "../../include/tools/atomic.h"
+
+#include "bench.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <sys/times.h>
+#include <sys/poll.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#include <linux/futex.h>
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include <poll.h>
+
+struct thread_barrier {
+	futex_t threads;
+	futex_t unblock;
+};
+
+struct worker_ctx {
+	futex_t *futex;
+	unsigned int iterations;
+
+	int readyfd, wakefd;
+
+	struct thread_barrier *barrier_before, *barrier_after;
+};
+
+static void fdpair(int fds[2])
+{
+	if (pipe(fds) == 0)
+		return;
+
+	die("pipe() failed");
+}
+
+static inline void futex_wait_lock(futex_t *futex)
+{
+	int status = *futex;
+	if (status == 0)
+		status = futex_cmpxchg(futex, 0, 1);
+	while (status != 0) {
+		if (status == 1)
+			status = futex_cmpxchg(futex, 1, 2);
+		if (status != 0) {
+			futex_wait(futex, 2, NULL, FUTEX_PRIVATE_FLAG);
+			status = *futex;
+		}
+		if (status == 0)
+			status = futex_cmpxchg(futex, 0, 2);
+	}
+}
+
+static inline void futex_cmpxchg_unlock(futex_t *futex)
+{
+	int status = *futex;
+	if (status == 1)
+		status = futex_cmpxchg(futex, 1, 0);
+	if (status == 2) {
+		futex_cmpxchg(futex, 2, 0);
+		futex_wake(futex, 1, FUTEX_PRIVATE_FLAG);
+	}
+}
+
+/* Called by main thread to initialize barrier */
+static void barrier_init(struct thread_barrier *barrier, int threads)
+{
+	barrier->threads = threads;
+	barrier->unblock = 0;
+}
+
+/* Called by worker threads to synchronize with main thread */
+static int barrier_sync(struct thread_barrier *barrier)
+{
+	futex_dec(&barrier->threads);
+	if (barrier->threads == 0)
+		futex_wake(&barrier->threads, 1, FUTEX_PRIVATE_FLAG);
+	while (barrier->unblock == 0)
+		futex_wait(&barrier->unblock, 0, NULL, FUTEX_PRIVATE_FLAG);
+	return barrier->unblock;
+}
+
+/* Called by main thread to wait for all workers to reach sync point */
+static void barrier_wait(struct thread_barrier *barrier)
+{
+	int threads;
+	while ((threads = barrier->threads) > 0)
+		futex_wait(&barrier->threads, threads, NULL,
+			   FUTEX_PRIVATE_FLAG);
+}
+
+/* Called by main thread to unblock worker threads from their sync point */
+static void barrier_unblock(struct thread_barrier *barrier, int value)
+{
+	barrier->unblock = value;
+	futex_wake(&barrier->unblock, INT_MAX, FUTEX_PRIVATE_FLAG);
+}
+
+static bool use_futex_for_sync;
+
+static void *worker(void *arg)
+{
+	char dummy;
+	int iterations;
+	futex_t *futex;
+
+	struct worker_ctx *ctx = (struct worker_ctx *)arg;
+	struct pollfd pollfd = { .fd = ctx->wakefd, .events = POLLIN };
+
+	iterations = ctx->iterations;
+	futex = ctx->futex;
+	/* currently, we have nothing to prepare */
+	if (use_futex_for_sync) {
+		barrier_sync(ctx->barrier_before);
+	} else {
+		if (write(ctx->readyfd, &dummy, 1) != 1)
+			die("write() on readyfd failed");
+
+		if (poll(&pollfd, 1, -1) != 1)
+			die("poll() failed");
+	}
+
+	while (iterations--) {
+		futex_wait_lock(futex);
+		futex_cmpxchg_unlock(futex);
+	}
+
+	if (use_futex_for_sync)
+		barrier_sync(ctx->barrier_after);
+
+	return NULL;
+}
+
+static int iterations = 100000000;
+static int threads = 256;
+/* futexes are fairly distributed for threads */
+static int futexes = 1;
+
+static const struct option options[] = {
+	OPT_INTEGER('i', "iterations", &iterations,
+		    "number of locking and unlocking"),
+	OPT_INTEGER('t', "threads", &threads,
+		    "number of worker threads"),
+	OPT_INTEGER('f', "futexes", &futexes,
+		"number of futexes, the condition"
+		"threads % futexes == 0 must be true"),
+	OPT_BOOLEAN('s', "futex-for-sync", &use_futex_for_sync,
+		"use futex for sync between main thread and worker threads"),
+	OPT_END()
+};
+
+static const char * const bench_futex_wait_usage[] = {
+	"perf bench futex wait <options>",
+	NULL
+};
+
+int bench_futex_wait(int argc, const char **argv,
+		const char *prefix __maybe_unused)
+{
+	int i;
+	char buf;
+	int wakefds[2], readyfds[2];
+	pthread_t *pth_tab;
+	struct worker_ctx *ctx_tab;
+	futex_t *futex_tab;
+
+	struct thread_barrier barrier_before, barrier_after;
+
+	clock_t before, after;
+	struct tms tms_before, tms_after;
+	int wall, user, system_time;
+	double tick;
+
+	argc = parse_options(argc, argv, options,
+			     bench_futex_wait_usage, 0);
+
+	if (threads % futexes)
+		die("threads %% futexes must be 0");
+
+	if (use_futex_for_sync) {
+		barrier_init(&barrier_before, threads);
+		barrier_init(&barrier_after, threads);
+	} else {
+		fdpair(wakefds);
+		fdpair(readyfds);
+	}
+
+	pth_tab = calloc(sizeof(pthread_t), threads);
+	if (!pth_tab)
+		die("calloc() for pthread descriptors failed");
+	ctx_tab = calloc(sizeof(struct worker_ctx), threads);
+	if (!ctx_tab)
+		die("calloc() for worker contexts failed");
+	futex_tab = calloc(sizeof(futex_t), futexes);
+	if (!futex_tab)
+		die("calloc() for futexes failed");
+
+	for (i = 0; i < threads; i++) {
+		ctx_tab[i].futex = &futex_tab[i % futexes];
+		ctx_tab[i].iterations = iterations / threads;
+
+		ctx_tab[i].readyfd = readyfds[1];
+		ctx_tab[i].wakefd = wakefds[0];
+
+		if (use_futex_for_sync) {
+			ctx_tab[i].barrier_before = &barrier_before;
+			ctx_tab[i].barrier_after = &barrier_after;
+		}
+
+		if (pthread_create(&pth_tab[i], NULL, worker, &ctx_tab[i]))
+			die("pthread_create() for creating workers failed");
+	}
+
+	if (use_futex_for_sync) {
+		barrier_wait(&barrier_before);
+	} else {
+		for (i = 0; i < threads; i++) {
+			if (read(readyfds[0], &buf, 1) != 1)
+				die("read() for ready failed");
+		}
+	}
+
+	before = times(&tms_before);
+
+	if (use_futex_for_sync) {
+		barrier_unblock(&barrier_before, 1);
+	} else {
+		if (write(wakefds[1], &buf, 1) != 1)
+			die("write() for waking up workers failed");
+	}
+
+	if (use_futex_for_sync) {
+		barrier_wait(&barrier_after);
+	} else {
+		for (i = 0; i < threads; i++)
+			pthread_join(pth_tab[i], NULL);
+	}
+
+	after = times(&tms_after);
+
+	wall = after - before;
+	user = tms_after.tms_utime - tms_before.tms_utime;
+	system_time = tms_after.tms_stime - tms_before.tms_stime;
+	tick = 1.0 / sysconf(_SC_CLK_TCK);
+
+	switch (bench_format) {
+	case BENCH_FORMAT_DEFAULT:
+		printf("# %d threads and %d futexes (%d threads for 1 futex)\n",
+			threads, futexes, threads / futexes);
+		printf("%.2fs user, %.2fs system, %.2fs wall, %.2f cores\n",
+			user * tick, system_time * tick, wall * tick,
+			wall ? (user + system_time) * 1. / wall : 1.);
+		printf("Result: %.0f Kiter/s\n",
+			iterations / (wall * tick * 1000));
+		break;
+	case BENCH_FORMAT_SIMPLE:
+		printf("%.0f Kiter/s\n",
+			iterations / (wall * tick * 1000));
+		break;
+	default:
+		/* reaching here is something disaster */
+		die("Unknown format:%d\n", bench_format);
+		break;
+	}
+
+	free((void *)pth_tab);
+	free((void *)ctx_tab);
+	free((void *)futex_tab);
+
+	return 0;
+}
diff --git a/tools/perf/builtin-bench.c b/tools/perf/builtin-bench.c
index cae9a5f..0533736 100644
--- a/tools/perf/builtin-bench.c
+++ b/tools/perf/builtin-bench.c
@@ -61,6 +61,16 @@ static struct bench_suite mem_suites[] = {
 	  NULL             }
 };
 
+static struct bench_suite futex_suites[] = {
+	{ "wait",
+	  "futex wait",
+	  bench_futex_wait },
+	suite_all,
+	{ NULL,
+	  NULL,
+	  NULL             }
+};
+
 struct bench_subsys {
 	const char *name;
 	const char *summary;
@@ -74,6 +84,9 @@ static struct bench_subsys subsystems[] = {
 	{ "mem",
 	  "memory access performance",
 	  mem_suites },
+	{ "futex",
+	  "futex performance",
+	  futex_suites },
 	{ "all",		/* sentinel: easy for help */
 	  "all benchmark subsystem",
 	  NULL },
-- 
1.7.5.1