summaryrefslogtreecommitdiff
path: root/tools/perf/bench/futex-requeue.c
diff options
context:
space:
mode:
authorDavidlohr Bueso <davidlohr@hp.com>2013-12-14 20:31:57 -0800
committerArnaldo Carvalho de Melo <acme@redhat.com>2014-03-14 11:20:44 -0300
commit0fb298cf95c0d8119557b7d4657724a146e0622e (patch)
tree373a4bd7d4117fd6e49d0750fb709368631594e5 /tools/perf/bench/futex-requeue.c
parent27db78307481dbba68c5f3563c6cb694b25521d9 (diff)
downloadlinux-0fb298cf95c0d8119557b7d4657724a146e0622e.tar.gz
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>
Diffstat (limited to 'tools/perf/bench/futex-requeue.c')
-rw-r--r--tools/perf/bench/futex-requeue.c211
1 files changed, 211 insertions, 0 deletions
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);
+}