perf bench: Add futex-hash microbenchmark

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>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <Waiman.Long@hp.com>
Link: http://lkml.kernel.org/r/1387081917-9102-2-git-send-email-davidlohr@hp.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

3 files changed, 261 insertions, 0 deletions

diff --git a/tools/perf/bench/bench.h b/tools/perf/bench/bench.h
index 0fdc85269c4d..34edb5c34db3 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 000000000000..a84206e9c4aa
--- /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 000000000000..7d0bda543e3d
--- /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 */