perf bench futex: Support parallel waker threads
authorDavidlohr Bueso <dave@stgolabs.net>
Fri, 8 May 2015 18:37:59 +0000 (11:37 -0700)
committerArnaldo Carvalho de Melo <acme@redhat.com>
Fri, 8 May 2015 19:23:50 +0000 (16:23 -0300)
The futex-wake benchmark only measures wakeups done within a single
process. While this has value in its own, it does not really generate
any hb->lock contention.

A new benchmark 'wake-parallel' is added, by extending the futex-wake
code such that we can measure parallel waker threads. The program output
shows the avg per-thread latency in order to complete its share of
wakeups:

Run summary [PID 13474]: blocking on 512 threads (at [private] futex 0xa88668), 8 threads waking up 64 at a time.

[Run 1]: Avg per-thread latency (waking 64/512 threads) in 0.6230 ms (+-15.31%)
[Run 2]: Avg per-thread latency (waking 64/512 threads) in 0.5175 ms (+-29.95%)
[Run 3]: Avg per-thread latency (waking 64/512 threads) in 0.7578 ms (+-18.03%)
[Run 4]: Avg per-thread latency (waking 64/512 threads) in 0.8944 ms (+-12.54%)
[Run 5]: Avg per-thread latency (waking 64/512 threads) in 1.1204 ms (+-23.85%)
Avg per-thread latency (waking 64/512 threads) in 0.7826 ms (+-9.91%)

Naturally, different combinations of numbers of blocking and waker
threads will exhibit different information.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Davidlohr Bueso <dbueso@suse.de>
Link: http://lkml.kernel.org/r/1431110280-20231-1-git-send-email-dave@stgolabs.net
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
tools/perf/Documentation/perf-bench.txt
tools/perf/bench/Build
tools/perf/bench/bench.h
tools/perf/bench/futex-wake-parallel.c [new file with mode: 0644]
tools/perf/builtin-bench.c

index f6480cbf309b40fee97e86112033c1a0cf04236a..bf3d0644bf1066677ae6ced215f82ecbc55f409d 100644 (file)
@@ -210,6 +210,9 @@ Suite for evaluating hash tables.
 *wake*::
 Suite for evaluating wake calls.
 
+*wake-parallel*::
+Suite for evaluating parallel wake calls.
+
 *requeue*::
 Suite for evaluating requeue calls.
 
index 5ce98023d518fce2d51ee11e35b0a0f2df12d8de..c3ab760e06b4d7627896723dc9fe2b15c5327a0b 100644 (file)
@@ -3,6 +3,7 @@ perf-y += sched-pipe.o
 perf-y += mem-memcpy.o
 perf-y += futex-hash.o
 perf-y += futex-wake.o
+perf-y += futex-wake-parallel.o
 perf-y += futex-requeue.o
 
 perf-$(CONFIG_X86_64) += mem-memcpy-x86-64-asm.o
index 3c4dd44d45cb7b668bd22822b6f105c1de9eaf86..70b2f718cc217976ee73bd656d66b9aa884dfded 100644 (file)
@@ -33,6 +33,8 @@ 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_wake_parallel(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"
diff --git a/tools/perf/bench/futex-wake-parallel.c b/tools/perf/bench/futex-wake-parallel.c
new file mode 100644 (file)
index 0000000..6d8c9fa
--- /dev/null
@@ -0,0 +1,294 @@
+/*
+ * Copyright (C) 2015 Davidlohr Bueso.
+ *
+ * Block a bunch of threads and let parallel waker threads wakeup an
+ * equal amount of them. The program output reflects the avg latency
+ * for each individual thread to service its share of work. Ultimately
+ * it can be used to measure futex_wake() changes.
+ */
+
+#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>
+
+struct thread_data {
+       pthread_t worker;
+       unsigned int nwoken;
+       struct timeval runtime;
+};
+
+static unsigned int nwakes = 1;
+
+/* all threads will block on the same futex -- hash bucket chaos ;) */
+static u_int32_t futex = 0;
+
+static pthread_t *blocked_worker;
+static bool done = false, silent = false, fshared = false;
+static unsigned int nblocked_threads = 0, nwaking_threads = 0;
+static pthread_mutex_t thread_lock;
+static pthread_cond_t thread_parent, thread_worker;
+static struct stats waketime_stats, wakeup_stats;
+static unsigned int ncpus, threads_starting;
+static int futex_flag = 0;
+
+static const struct option options[] = {
+       OPT_UINTEGER('t', "threads", &nblocked_threads, "Specify amount of threads"),
+       OPT_UINTEGER('w', "nwakers", &nwaking_threads, "Specify amount of waking 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_wake_parallel_usage[] = {
+       "perf bench futex wake-parallel <options>",
+       NULL
+};
+
+static void *waking_workerfn(void *arg)
+{
+       struct thread_data *waker = (struct thread_data *) arg;
+       struct timeval start, end;
+
+       gettimeofday(&start, NULL);
+
+       waker->nwoken = futex_wake(&futex, nwakes, futex_flag);
+       if (waker->nwoken != nwakes)
+               warnx("couldn't wakeup all tasks (%d/%d)",
+                     waker->nwoken, nwakes);
+
+       gettimeofday(&end, NULL);
+       timersub(&end, &start, &waker->runtime);
+
+       pthread_exit(NULL);
+       return NULL;
+}
+
+static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr)
+{
+       unsigned int i;
+
+       pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE);
+
+       /* create and block all threads */
+       for (i = 0; i < nwaking_threads; i++) {
+               /*
+                * Thread creation order will impact per-thread latency
+                * as it will affect the order to acquire the hb spinlock.
+                * For now let the scheduler decide.
+                */
+               if (pthread_create(&td[i].worker, &thread_attr,
+                                  waking_workerfn, (void *)&td[i]))
+                       err(EXIT_FAILURE, "pthread_create");
+       }
+
+       for (i = 0; i < nwaking_threads; i++)
+               if (pthread_join(td[i].worker, NULL))
+                       err(EXIT_FAILURE, "pthread_join");
+}
+
+static void *blocked_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);
+
+       while (1) { /* handle spurious wakeups */
+               if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR)
+                       break;
+       }
+
+       pthread_exit(NULL);
+       return NULL;
+}
+
+static void block_threads(pthread_t *w, pthread_attr_t thread_attr)
+{
+       cpu_set_t cpu;
+       unsigned int i;
+
+       threads_starting = nblocked_threads;
+
+       /* create and block all threads */
+       for (i = 0; i < nblocked_threads; 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, blocked_workerfn, NULL))
+                       err(EXIT_FAILURE, "pthread_create");
+       }
+}
+
+static void print_run(struct thread_data *waking_worker, unsigned int run_num)
+{
+       unsigned int i, wakeup_avg;
+       double waketime_avg, waketime_stddev;
+       struct stats __waketime_stats, __wakeup_stats;
+
+       init_stats(&__wakeup_stats);
+       init_stats(&__waketime_stats);
+
+       for (i = 0; i < nwaking_threads; i++) {
+               update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec);
+               update_stats(&__wakeup_stats, waking_worker[i].nwoken);
+       }
+
+       waketime_avg = avg_stats(&__waketime_stats);
+       waketime_stddev = stddev_stats(&__waketime_stats);
+       wakeup_avg = avg_stats(&__wakeup_stats);
+
+       printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) "
+              "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg,
+              nblocked_threads, waketime_avg/1e3,
+              rel_stddev_stats(waketime_stddev, waketime_avg));
+}
+
+static void print_summary(void)
+{
+       unsigned int wakeup_avg;
+       double waketime_avg, waketime_stddev;
+
+       waketime_avg = avg_stats(&waketime_stats);
+       waketime_stddev = stddev_stats(&waketime_stats);
+       wakeup_avg = avg_stats(&wakeup_stats);
+
+       printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n",
+              wakeup_avg,
+              nblocked_threads,
+              waketime_avg/1e3,
+              rel_stddev_stats(waketime_stddev, waketime_avg));
+}
+
+
+static void do_run_stats(struct thread_data *waking_worker)
+{
+       unsigned int i;
+
+       for (i = 0; i < nwaking_threads; i++) {
+               update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec);
+               update_stats(&wakeup_stats, waking_worker[i].nwoken);
+       }
+
+}
+
+static void toggle_done(int sig __maybe_unused,
+                       siginfo_t *info __maybe_unused,
+                       void *uc __maybe_unused)
+{
+       done = true;
+}
+
+int bench_futex_wake_parallel(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;
+       struct thread_data *waking_worker;
+
+       argc = parse_options(argc, argv, options,
+                            bench_futex_wake_parallel_usage, 0);
+       if (argc) {
+               usage_with_options(bench_futex_wake_parallel_usage, options);
+               exit(EXIT_FAILURE);
+       }
+
+       sigfillset(&act.sa_mask);
+       act.sa_sigaction = toggle_done;
+       sigaction(SIGINT, &act, NULL);
+
+       ncpus = sysconf(_SC_NPROCESSORS_ONLN);
+       if (!nblocked_threads)
+               nblocked_threads = ncpus;
+
+       /* some sanity checks */
+       if (nwaking_threads > nblocked_threads || !nwaking_threads)
+               nwaking_threads = nblocked_threads;
+
+       if (nblocked_threads % nwaking_threads)
+               errx(EXIT_FAILURE, "Must be perfectly divisible");
+       /*
+        * Each thread will wakeup nwakes tasks in
+        * a single futex_wait call.
+        */
+       nwakes = nblocked_threads/nwaking_threads;
+
+       blocked_worker = calloc(nblocked_threads, sizeof(*blocked_worker));
+       if (!blocked_worker)
+               err(EXIT_FAILURE, "calloc");
+
+       if (!fshared)
+               futex_flag = FUTEX_PRIVATE_FLAG;
+
+       printf("Run summary [PID %d]: blocking on %d threads (at [%s] "
+              "futex %p), %d threads waking up %d at a time.\n\n",
+              getpid(), nblocked_threads, fshared ? "shared":"private",
+              &futex, nwaking_threads, nwakes);
+
+       init_stats(&wakeup_stats);
+       init_stats(&waketime_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 < bench_repeat && !done; j++) {
+               waking_worker = calloc(nwaking_threads, sizeof(*waking_worker));
+               if (!waking_worker)
+                       err(EXIT_FAILURE, "calloc");
+
+               /* create, launch & block all threads */
+               block_threads(blocked_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 waking folks up */
+               wakeup_threads(waking_worker, thread_attr);
+
+               for (i = 0; i < nblocked_threads; i++) {
+                       ret = pthread_join(blocked_worker[i], NULL);
+                       if (ret)
+                               err(EXIT_FAILURE, "pthread_join");
+               }
+
+               do_run_stats(waking_worker);
+               if (!silent)
+                       print_run(waking_worker, j);
+
+               free(waking_worker);
+       }
+
+       /* 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(blocked_worker);
+       return ret;
+}
index b9a56fa8333065271a9242e98cf052d9c8100b87..b5314e452ec7f24a2e9e4e6b8473d39b8ed7a4a7 100644 (file)
@@ -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        },
+       { "wake-parallel", "Benchmark for parallel futex wake calls",   bench_futex_wake_parallel },
        { "requeue",    "Benchmark for futex requeue calls",            bench_futex_requeue     },
        { "all",        "Test all futex benchmarks",                    NULL                    },
        { NULL,         NULL,                                           NULL                    }