perf bench: Add futex-requeue microbenchmark

Block a bunch of threads on a futex and requeue them on another, N at a
time.

This program is particularly useful to measure the latency of nthread
requeues without waking up any tasks -- thus mimicking a regular
futex_wait.

An example run:

  $ perf bench futex requeue -r 100 -t 64
  Run summary [PID 151011]: Requeuing 64 threads (from 0x7d15c4 to 0x7d15c8), 1 at a time.

  [Run 1]: Requeued 64 of 64 threads in 0.0400 ms
  [Run 2]: Requeued 64 of 64 threads in 0.0390 ms
  [Run 3]: Requeued 64 of 64 threads in 0.0400 ms
  ...
  [Run 100]: Requeued 64 of 64 threads in 0.0390 ms
  Requeued 64 of 64 threads in 0.0399 ms (+-0.37%)

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/1387081917-9102-4-git-send-email-davidlohr@hp.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

5 files changed, 227 insertions, 0 deletions

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 6fa5d8b74635..50d875d970c4 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -428,6 +428,7 @@ BUILTIN_OBJS += $(OUTPUT)bench/mem-memcpy.o
 BUILTIN_OBJS += $(OUTPUT)bench/mem-memset.o
 BUILTIN_OBJS += $(OUTPUT)bench/futex-hash.o
 BUILTIN_OBJS += $(OUTPUT)bench/futex-wake.o
+BUILTIN_OBJS += $(OUTPUT)bench/futex-requeue.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 6ac3f1d083cc..eba46709b279 100644
--- a/tools/perf/bench/bench.h
+++ b/tools/perf/bench/bench.h
@@ -33,6 +33,7 @@ extern int bench_mem_memcpy(int argc, const char **argv,
 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);
 extern int bench_futex_wake(int argc, const char **argv, const char *prefix);
+extern int bench_futex_requeue(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-requeue.c b/tools/perf/bench/futex-requeue.c
new file mode 100644
index 000000000000..a16255876f1d
--- /dev/null
+++ b/tools/perf/bench/futex-requeue.c
@@ -0,0 +1,211 @@
+/*
+ * Copyright (C) 2013  Davidlohr Bueso <davidlohr@hp.com>
+ *
+ * futex-requeue: Block a bunch of threads on futex1 and requeue them
+ *                on futex2, N at a time.
+ *
+ * This program is particularly useful to measure the latency of nthread
+ * requeues without waking up any tasks -- thus mimicking a regular futex_wait.
+ */
+
+#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 u_int32_t futex1 = 0, futex2 = 0;
+
+/*
+ * How many tasks to requeue at a time.
+ * Default to 1 in order to make the kernel work more.
+ */
+static unsigned int nrequeue = 1;
+
+/*
+ * There can be significant variance from run to run,
+ * the more repeats, the more exact the overall avg and
+ * the better idea of the futex latency.
+ */
+static unsigned int repeat = 10;
+
+static pthread_t *worker;
+static bool done = 0, silent = 0;
+static pthread_mutex_t thread_lock;
+static pthread_cond_t thread_parent, thread_worker;
+static struct stats requeuetime_stats, requeued_stats;
+static unsigned int ncpus, threads_starting, nthreads = 0;
+
+static const struct option options[] = {
+        OPT_UINTEGER('t', "threads",  &nthreads, "Specify amount of threads"),
+        OPT_UINTEGER('q', "nrequeue", &nrequeue, "Specify amount of threads to requeue at once"),
+        OPT_UINTEGER('r', "repeat",   &repeat,   "Specify amount of times to repeat the run"),
+        OPT_BOOLEAN( 's', "silent",   &silent,   "Silent mode: do not display data/details"),
+        OPT_END()
+};
+
+static const char * const bench_futex_requeue_usage[] = {
+        "perf bench futex requeue <options>",
+        NULL
+};
+
+static void print_summary(void)
+{
+        double requeuetime_avg = avg_stats(&requeuetime_stats);
+        double requeuetime_stddev = stddev_stats(&requeuetime_stats);
+        unsigned int requeued_avg = avg_stats(&requeued_stats);
+
+        printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
+               requeued_avg,
+               nthreads,
+               requeuetime_avg/1e3,
+               rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
+}
+
+static void *workerfn(void *arg __maybe_unused)
+{
+        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);
+
+        futex_wait(&futex1, 0, NULL, FUTEX_PRIVATE_FLAG);
+        return NULL;
+}
+
+static void block_threads(pthread_t *w,
+                          pthread_attr_t thread_attr)
+{
+        cpu_set_t cpu;
+        unsigned int i;
+
+        threads_starting = nthreads;
+
+        /* create and block all threads */
+        for (i = 0; i < nthreads; i++) {
+                CPU_ZERO(&cpu);
+                CPU_SET(i % ncpus, &cpu);
+
+                if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu))
+                        err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
+
+                if (pthread_create(&w[i], &thread_attr, workerfn, NULL))
+                        err(EXIT_FAILURE, "pthread_create");
+        }
+}
+
+static void toggle_done(int sig __maybe_unused,
+                        siginfo_t *info __maybe_unused,
+                        void *uc __maybe_unused)
+{
+        done = true;
+}
+
+int bench_futex_requeue(int argc, const char **argv,
+                        const char *prefix __maybe_unused)
+{
+        int ret = 0;
+        unsigned int i, j;
+        struct sigaction act;
+        pthread_attr_t thread_attr;
+
+        argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
+        if (argc)
+                goto err;
+
+        ncpus = sysconf(_SC_NPROCESSORS_ONLN);
+
+        sigfillset(&act.sa_mask);
+        act.sa_sigaction = toggle_done;
+        sigaction(SIGINT, &act, NULL);
+
+        if (!nthreads)
+                nthreads = ncpus;
+
+        worker = calloc(nthreads, sizeof(*worker));
+        if (!worker)
+                err(EXIT_FAILURE, "calloc");
+
+        printf("Run summary [PID %d]: Requeuing %d threads (from %p to %p), "
+               "%d at a time.\n\n",
+               getpid(), nthreads, &futex1, &futex2, nrequeue);
+
+        init_stats(&requeued_stats);
+        init_stats(&requeuetime_stats);
+        pthread_attr_init(&thread_attr);
+        pthread_mutex_init(&thread_lock, NULL);
+        pthread_cond_init(&thread_parent, NULL);
+        pthread_cond_init(&thread_worker, NULL);
+
+        for (j = 0; j < repeat && !done; j++) {
+                unsigned int nrequeued = 0;
+                struct timeval start, end, runtime;
+
+                /* create, launch & block all threads */
+                block_threads(worker, thread_attr);
+
+                /* make sure all threads are already blocked */
+                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);
+
+                usleep(100000);
+
+                /* Ok, all threads are patiently blocked, start requeueing */
+                gettimeofday(&start, NULL);
+                for (nrequeued = 0; nrequeued < nthreads; nrequeued += nrequeue)
+                        /*
+                         * Do not wakeup any tasks blocked on futex1, allowing
+                         * us to really measure futex_wait functionality.
+                         */
+                        futex_cmp_requeue(&futex1, 0, &futex2, 0, nrequeue,
+                                          FUTEX_PRIVATE_FLAG);
+                gettimeofday(&end, NULL);
+                timersub(&end, &start, &runtime);
+
+                update_stats(&requeued_stats, nrequeued);
+                update_stats(&requeuetime_stats, runtime.tv_usec);
+
+                if (!silent) {
+                        printf("[Run %d]: Requeued %d of %d threads in %.4f ms\n",
+                               j + 1, nrequeued, nthreads, runtime.tv_usec/1e3);
+                }
+
+                /* everybody should be blocked on futex2, wake'em up */
+                nrequeued = futex_wake(&futex2, nthreads, FUTEX_PRIVATE_FLAG);
+                if (nthreads != nrequeued)
+                        warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads);
+
+                for (i = 0; i < nthreads; i++) {
+                        ret = pthread_join(worker[i], 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);
+        pthread_attr_destroy(&thread_attr);
+
+        print_summary();
+
+        free(worker);
+        return ret;
+err:
+        usage_with_options(bench_futex_requeue_usage, options);
+        exit(EXIT_FAILURE);
+}
diff --git a/tools/perf/bench/futex.h b/tools/perf/bench/futex.h
index 6ac45093fac4..71f2844cf97f 100644
--- a/tools/perf/bench/futex.h
+++ b/tools/perf/bench/futex.h
@@ -55,4 +55,17 @@ futex_wake(u_int32_t *uaddr, int nr_wake, int opflags)
         return futex(uaddr, FUTEX_WAKE, nr_wake, NULL, NULL, 0, opflags);
 }
 
+/**
+* futex_cmp_requeue() - requeue tasks from uaddr to uaddr2
+* @nr_wake:        wake up to this many tasks
+* @nr_requeue:        requeue up to this many tasks
+*/
+static inline int
+futex_cmp_requeue(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2, int nr_wake,
+                 int nr_requeue, int opflags)
+{
+        return futex(uaddr, FUTEX_CMP_REQUEUE, nr_wake, nr_requeue, uaddr2,
+                 val, opflags);
+}
+
 #endif /* _FUTEX_H */
diff --git a/tools/perf/builtin-bench.c b/tools/perf/builtin-bench.c
index 743a30a8baa0..f600b74216da 100644
--- a/tools/perf/builtin-bench.c
+++ b/tools/perf/builtin-bench.c
@@ -58,6 +58,7 @@ static struct bench mem_benchmarks[] = {
 static struct bench futex_benchmarks[] = {
         { "hash",       "Benchmark for futex hash table",               bench_futex_hash        },
         { "wake",       "Benchmark for futex wake calls",               bench_futex_wake        },
+        { "requeue",    "Benchmark for futex requeue calls",            bench_futex_requeue     },
         { "all",        "Test all futex benchmarks",                    NULL                    },
         { NULL,         NULL,                                           NULL                    }
 };