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Subject[PATCH 1/3] perf-bench: add futex-hash microbenchmark
Date
Introduce futexes to perf-bench and add a program that stresses
and measures the kernel's implementation of the hash table.
This is a multi-threaded program that simply measures the amount
of failed futex wait calls - we only want to deal with the hashing
overhead, so a negative return of futex_wait_setup() is enough to
do the trick. An example run:

$ perf bench futex hash -t 32
Run summary [PID 10989]: 32 threads, each operating on 1024 [private] futexes for 10 secs.

[thread 0] futexes: 0x19d9b10 ... 0x19dab0c [ 418713 ops/sec ]
[thread 1] futexes: 0x19daca0 ... 0x19dbc9c [ 469913 ops/sec ]
[thread 2] futexes: 0x19dbe30 ... 0x19dce2c [ 479744 ops/sec ]
...
[thread 31] futexes: 0x19fbb80 ... 0x19fcb7c [ 464179 ops/sec ]

Averaged 454310 operations/sec (+- 0.84%), total secs = 10

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
---
tools/perf/Makefile.perf | 1 +
tools/perf/bench/bench.h | 1 +
tools/perf/bench/futex-hash.c | 212 ++++++++++++++++++++++++++++++++++++++++++
tools/perf/bench/futex.h | 48 ++++++++++
tools/perf/builtin-bench.c | 10 +-
tools/perf/perf.h | 6 ++
6 files changed, 277 insertions(+), 1 deletion(-)
create mode 100644 tools/perf/bench/futex-hash.c
create mode 100644 tools/perf/bench/futex.h

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 7fc8f17..c38cba4 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -416,6 +416,7 @@ 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-hash.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 0fdc852..34edb5c 100644
--- a/tools/perf/bench/bench.h
+++ b/tools/perf/bench/bench.h
@@ -31,6 +31,7 @@ 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_hash(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-hash.c b/tools/perf/bench/futex-hash.c
new file mode 100644
index 0000000..a84206e
--- /dev/null
+++ b/tools/perf/bench/futex-hash.c
@@ -0,0 +1,212 @@
+/*
+ * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com>
+ *
+ * futex-hash: Stress the hell out of the Linux kernel futex uaddr hashing.
+ *
+ * This program is particularly useful for measuring the kernel's futex hash
+ * table/function implementation. In order for it to make sense, use with as
+ * many threads and futexes as possible.
+ */
+
+#include "../perf.h"
+#include "../util/util.h"
+#include "../util/stat.h"
+#include "../util/parse-options.h"
+#include "../util/header.h"
+#include "bench.h"
+#include "futex.h"
+
+#include <err.h>
+#include <stdlib.h>
+#include <sys/time.h>
+#include <pthread.h>
+
+static unsigned int nthreads = 0;
+static unsigned int nsecs = 10;
+/* amount of futexes per thread */
+static unsigned int nfutexes = 1024;
+static bool fshared = false, done = false, silent = false;
+
+struct timeval start, end, runtime;
+static pthread_mutex_t thread_lock;
+static unsigned int threads_starting;
+static struct stats throughput_stats;
+static pthread_cond_t thread_parent, thread_worker;
+
+struct worker {
+ int tid;
+ u_int32_t *futex;
+ pthread_t thread;
+ unsigned long ops;
+};
+
+static const struct option options[] = {
+ OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
+ OPT_UINTEGER('r', "runtime", &nsecs, "Specify runtime (in seconds)"),
+ OPT_UINTEGER('f', "futexes", &nfutexes, "Specify amount of futexes per threads"),
+ OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"),
+ OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"),
+ OPT_END()
+};
+
+static const char * const bench_futex_hash_usage[] = {
+ "perf bench futex hash <options>",
+ NULL
+};
+
+static void *workerfn(void *arg)
+{
+ int ret;
+ unsigned int i;
+ struct worker *w = (struct worker *) arg;
+
+ pthread_mutex_lock(&thread_lock);
+ threads_starting--;
+ if (!threads_starting)
+ pthread_cond_signal(&thread_parent);
+ pthread_cond_wait(&thread_worker, &thread_lock);
+ pthread_mutex_unlock(&thread_lock);
+
+ do {
+ for (i = 0; i < nfutexes; i++, w->ops++) {
+ /*
+ * We want the futex calls to fail in order to stress
+ * the hashing of uaddr and not measure other steps,
+ * such as internal waitqueue handling, thus enlarging
+ * the critical region protected by hb->lock.
+ */
+ ret = futex_wait(&w->futex[i], 1234, NULL,
+ fshared ? 0 : FUTEX_PRIVATE_FLAG);
+ if (!silent &&
+ (!ret || errno != EAGAIN || errno != EWOULDBLOCK))
+ warn("Non-expected futex return call");
+ }
+ } while (!done);
+
+ return NULL;
+}
+
+static void toggle_done(int sig __maybe_unused,
+ siginfo_t *info __maybe_unused,
+ void *uc __maybe_unused)
+{
+ /* inform all threads that we're done for the day */
+ done = true;
+ gettimeofday(&end, NULL);
+ timersub(&end, &start, &runtime);
+}
+
+static void print_summary(void)
+{
+ unsigned long avg = avg_stats(&throughput_stats);
+ double stddev = stddev_stats(&throughput_stats);
+
+ printf("%sAveraged %ld operations/sec (+- %.2f%%), total secs = %d\n",
+ !silent ? "\n" : "", avg, rel_stddev_stats(stddev, avg),
+ (int) runtime.tv_sec);
+}
+
+int bench_futex_hash(int argc, const char **argv,
+ const char *prefix __maybe_unused)
+{
+ int ret = 0;
+ cpu_set_t cpu;
+ struct sigaction act;
+ unsigned int i, ncpus;
+ pthread_attr_t thread_attr;
+ struct worker *worker = NULL;
+
+ argc = parse_options(argc, argv, options, bench_futex_hash_usage, 0);
+ if (argc) {
+ usage_with_options(bench_futex_hash_usage, options);
+ exit(EXIT_FAILURE);
+ }
+
+ ncpus = sysconf(_SC_NPROCESSORS_ONLN);
+
+ sigfillset(&act.sa_mask);
+ act.sa_sigaction = toggle_done;
+ sigaction(SIGINT, &act, NULL);
+
+ if (!nthreads) /* default to the number of CPUs */
+ nthreads = ncpus;
+
+ worker = calloc(nthreads, sizeof(*worker));
+ if (!worker)
+ goto errmem;
+
+ printf("Run summary [PID %d]: %d threads, each operating on %d [%s] futexes for %d secs.\n\n",
+ getpid(), nthreads, nfutexes, fshared ? "shared":"private", nsecs);
+
+ init_stats(&throughput_stats);
+ pthread_mutex_init(&thread_lock, NULL);
+ pthread_cond_init(&thread_parent, NULL);
+ pthread_cond_init(&thread_worker, NULL);
+
+ threads_starting = nthreads;
+ pthread_attr_init(&thread_attr);
+ gettimeofday(&start, NULL);
+ for (i = 0; i < nthreads; i++) {
+ worker[i].tid = i;
+ worker[i].futex = calloc(nfutexes, sizeof(*worker[i].futex));
+ if (!worker[i].futex)
+ goto errmem;
+
+ CPU_ZERO(&cpu);
+ CPU_SET(i % ncpus, &cpu);
+
+ ret = pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu);
+ if (ret)
+ err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
+
+ ret = pthread_create(&worker[i].thread, &thread_attr, workerfn,
+ (void *)(struct worker *) &worker[i]);
+ if (ret)
+ err(EXIT_FAILURE, "pthread_create");
+
+ }
+ pthread_attr_destroy(&thread_attr);
+
+ pthread_mutex_lock(&thread_lock);
+ while (threads_starting)
+ pthread_cond_wait(&thread_parent, &thread_lock);
+ pthread_cond_broadcast(&thread_worker);
+ pthread_mutex_unlock(&thread_lock);
+
+ sleep(nsecs);
+ toggle_done(0, NULL, NULL);
+
+ for (i = 0; i < nthreads; i++) {
+ ret = pthread_join(worker[i].thread, NULL);
+ if (ret)
+ err(EXIT_FAILURE, "pthread_join");
+ }
+
+ /* cleanup & report results */
+ pthread_cond_destroy(&thread_parent);
+ pthread_cond_destroy(&thread_worker);
+ pthread_mutex_destroy(&thread_lock);
+
+ for (i = 0; i < nthreads; i++) {
+ unsigned long t = worker[i].ops/runtime.tv_sec;
+ update_stats(&throughput_stats, t);
+ if (!silent) {
+ if (nfutexes == 1)
+ printf("[thread %2d] futex: %p [ %ld ops/sec ]\n",
+ worker[i].tid, &worker[i].futex[0], t);
+ else
+ printf("[thread %2d] futexes: %p ... %p [ %ld ops/sec ]\n",
+ worker[i].tid, &worker[i].futex[0],
+ &worker[i].futex[nfutexes-1], t);
+ }
+
+ free(worker[i].futex);
+ }
+
+ print_summary();
+
+ free(worker);
+ return ret;
+errmem:
+ err(EXIT_FAILURE, "calloc");
+}
diff --git a/tools/perf/bench/futex.h b/tools/perf/bench/futex.h
new file mode 100644
index 0000000..7d0bda5
--- /dev/null
+++ b/tools/perf/bench/futex.h
@@ -0,0 +1,48 @@
+/*
+ * Glibc independent futex library for testing kernel functionality.
+ * Shamelessly stolen from Darren Hart <dvhltc@us.ibm.com>
+ * http://git.kernel.org/cgit/linux/kernel/git/dvhart/futextest.git/
+ */
+
+#ifndef _FUTEX_H
+#define _FUTEX_H
+
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <linux/futex.h>
+
+/**
+ * futex() - SYS_futex syscall wrapper
+ * @uaddr: address of first futex
+ * @op: futex op code
+ * @val: typically expected value of uaddr, but varies by op
+ * @timeout: typically an absolute struct timespec (except where noted
+ * otherwise). Overloaded by some ops
+ * @uaddr2: address of second futex for some ops\
+ * @val3: varies by op
+ * @opflags: flags to be bitwise OR'd with op, such as FUTEX_PRIVATE_FLAG
+ *
+ * futex() is used by all the following futex op wrappers. It can also be
+ * used for misuse and abuse testing. Generally, the specific op wrappers
+ * should be used instead. It is a macro instead of an static inline function as
+ * some of the types over overloaded (timeout is used for nr_requeue for
+ * example).
+ *
+ * These argument descriptions are the defaults for all
+ * like-named arguments in the following wrappers except where noted below.
+ */
+#define futex(uaddr, op, val, timeout, uaddr2, val3, opflags) \
+ syscall(SYS_futex, uaddr, op | opflags, val, timeout, uaddr2, val3)
+
+/**
+ * futex_wait() - block on uaddr with optional timeout
+ * @timeout: relative timeout
+ */
+static inline int
+futex_wait(u_int32_t *uaddr, u_int32_t val, struct timespec *timeout, int opflags)
+{
+ return futex(uaddr, FUTEX_WAIT, val, timeout, NULL, 0, opflags);
+}
+
+#endif /* _FUTEX_H */
diff --git a/tools/perf/builtin-bench.c b/tools/perf/builtin-bench.c
index e47f90c..a8b0138 100644
--- a/tools/perf/builtin-bench.c
+++ b/tools/perf/builtin-bench.c
@@ -12,6 +12,7 @@
* sched ... scheduler and IPC performance
* mem ... memory access performance
* numa ... NUMA scheduling and MM performance
+ * futex ... Futex performance
*/
#include "perf.h"
#include "util/util.h"
@@ -54,6 +55,12 @@ static struct bench mem_benchmarks[] = {
{ NULL, NULL, NULL }
};

+static struct bench futex_benchmarks[] = {
+ { "hash", "Benchmark for futex hash table", bench_futex_hash },
+ { "all", "Test all futex benchmarks", NULL },
+ { NULL, NULL, NULL }
+};
+
struct collection {
const char *name;
const char *summary;
@@ -61,11 +68,12 @@ struct collection {
};

static struct collection collections[] = {
- { "sched", "Scheduler and IPC benchmarks", sched_benchmarks },
+ { "sched", "Scheduler and IPC benchmarks", sched_benchmarks },
{ "mem", "Memory access benchmarks", mem_benchmarks },
#ifdef HAVE_LIBNUMA_SUPPORT
{ "numa", "NUMA scheduling and MM benchmarks", numa_benchmarks },
#endif
+ {"futex", "Futex stressing benchmarks", futex_benchmarks },
{ "all", "All benchmarks", NULL },
{ NULL, NULL, NULL }
};
diff --git a/tools/perf/perf.h b/tools/perf/perf.h
index b079304..e97caee 100644
--- a/tools/perf/perf.h
+++ b/tools/perf/perf.h
@@ -12,6 +12,9 @@
#ifndef __NR_perf_event_open
# define __NR_perf_event_open 336
#endif
+#ifndef __NR_futex
+# define __NR_futex 240
+#endif
#endif

#if defined(__x86_64__)
@@ -23,6 +26,9 @@
#ifndef __NR_perf_event_open
# define __NR_perf_event_open 298
#endif
+#ifndef __NR_futex
+# define __NR_futex 202
+#endif
#endif

#ifdef __powerpc__
--
1.8.1.4


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