From 46f815323b5a8f0e7156f50ea87c354424210e97 Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Sun, 8 Aug 2021 21:33:01 -0700 Subject: [PATCH] perf bench futex, requeue: Add --pi parameter This extends the program to measure WAIT_REQUEUE_PI+CMP_REQUEUE_PI pairs, which are the underlying machinery behind priority-inheritance aware condition variables. The defaults are the same as with the regular non-pi version, requeueing one task at a time, with the exception that PI will always wakeup the first waiter. Signed-off-by: Davidlohr Bueso Cc: Davidlohr Bueso Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lore.kernel.org/lkml/20210809043301.66002-8-dave@stgolabs.net Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/bench/futex-requeue.c | 100 +++++++++++++++++++++++++++++---------- tools/perf/bench/futex.h | 37 ++++++++++++++- 2 files changed, 111 insertions(+), 26 deletions(-) diff --git a/tools/perf/bench/futex-requeue.c b/tools/perf/bench/futex-requeue.c index e23a080..97fe31f 100644 --- a/tools/perf/bench/futex-requeue.c +++ b/tools/perf/bench/futex-requeue.c @@ -6,7 +6,8 @@ * 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. + * requeues without waking up any tasks (in the non-pi case) -- thus + * mimicking a regular futex_wait. */ /* For the CLR_() macros */ @@ -54,6 +55,8 @@ static const struct option options[] = { OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"), OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"), OPT_BOOLEAN( 'B', "broadcast", ¶ms.broadcast, "Requeue all threads at once"), + OPT_BOOLEAN( 'p', "pi", ¶ms.pi, "Use PI-aware variants of FUTEX_CMP_REQUEUE"), + OPT_END() }; @@ -87,14 +90,30 @@ static void *workerfn(void *arg __maybe_unused) pthread_mutex_unlock(&thread_lock); while (1) { - ret = futex_wait(&futex1, 0, NULL, futex_flag); - if (!ret) - break; - - if (ret && errno != EAGAIN) { - if (!params.silent) - warn("futex_wait"); - break; + if (!params.pi) { + ret = futex_wait(&futex1, 0, NULL, futex_flag); + if (!ret) + break; + + if (ret && errno != EAGAIN) { + if (!params.silent) + warnx("futex_wait"); + break; + } + } else { + ret = futex_wait_requeue_pi(&futex1, 0, &futex2, + NULL, futex_flag); + if (!ret) { + /* got the lock at futex2 */ + futex_unlock_pi(&futex2, futex_flag); + break; + } + + if (ret && errno != EAGAIN) { + if (!params.silent) + warnx("futex_wait_requeue_pi"); + break; + } } } @@ -171,9 +190,10 @@ int bench_futex_requeue(int argc, const char **argv) if (params.broadcast) params.nrequeue = params.nthreads; - printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %p), " + printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), " "%d at a time.\n\n", getpid(), params.nthreads, - params.fshared ? "shared":"private", &futex1, &futex2, params.nrequeue); + params.fshared ? "shared":"private", &futex1, + params.pi ? "PI ": "", &futex2, params.nrequeue); init_stats(&requeued_stats); init_stats(&requeuetime_stats); @@ -183,7 +203,7 @@ int bench_futex_requeue(int argc, const char **argv) pthread_cond_init(&thread_worker, NULL); for (j = 0; j < bench_repeat && !done; j++) { - unsigned int nrequeued = 0; + unsigned int nrequeued = 0, wakeups = 0; struct timeval start, end, runtime; /* create, launch & block all threads */ @@ -201,13 +221,30 @@ int bench_futex_requeue(int argc, const char **argv) /* Ok, all threads are patiently blocked, start requeueing */ gettimeofday(&start, NULL); while (nrequeued < params.nthreads) { + int r; + /* - * Do not wakeup any tasks blocked on futex1, allowing - * us to really measure futex_wait functionality. + * For the regular non-pi case, do not wakeup any tasks + * blocked on futex1, allowing us to really measure + * futex_wait functionality. For the PI case the first + * waiter is always awoken. */ - nrequeued += futex_cmp_requeue(&futex1, 0, &futex2, 0, - params.nrequeue, - futex_flag); + if (!params.pi) { + r = futex_cmp_requeue(&futex1, 0, &futex2, 0, + params.nrequeue, + futex_flag); + } else { + r = futex_cmp_requeue_pi(&futex1, 0, &futex2, + params.nrequeue, + futex_flag); + wakeups++; /* assume no error */ + } + + if (r < 0) + err(EXIT_FAILURE, "couldn't requeue from %p to %p", + &futex1, &futex2); + + nrequeued += r; } gettimeofday(&end, NULL); @@ -217,16 +254,29 @@ int bench_futex_requeue(int argc, const char **argv) update_stats(&requeuetime_stats, runtime.tv_usec); if (!params.silent) { - printf("[Run %d]: Requeued %d of %d threads in %.4f ms\n", - j + 1, nrequeued, params.nthreads, - runtime.tv_usec / (double)USEC_PER_MSEC); + if (!params.pi) + printf("[Run %d]: Requeued %d of %d threads in " + "%.4f ms\n", j + 1, nrequeued, + params.nthreads, + runtime.tv_usec / (double)USEC_PER_MSEC); + else { + nrequeued -= wakeups; + printf("[Run %d]: Awoke and Requeued (%d+%d) of " + "%d threads in %.4f ms\n", + j + 1, wakeups, nrequeued, + params.nthreads, + runtime.tv_usec / (double)USEC_PER_MSEC); + } + } - /* everybody should be blocked on futex2, wake'em up */ - nrequeued = futex_wake(&futex2, nrequeued, futex_flag); - if (params.nthreads != nrequeued) - warnx("couldn't wakeup all tasks (%d/%d)", - nrequeued, params.nthreads); + if (!params.pi) { + /* everybody should be blocked on futex2, wake'em up */ + nrequeued = futex_wake(&futex2, nrequeued, futex_flag); + if (params.nthreads != nrequeued) + warnx("couldn't wakeup all tasks (%d/%d)", + nrequeued, params.nthreads); + } for (i = 0; i < params.nthreads; i++) { ret = pthread_join(worker[i], NULL); diff --git a/tools/perf/bench/futex.h b/tools/perf/bench/futex.h index 40a89f1..b3853aa 100644 --- a/tools/perf/bench/futex.h +++ b/tools/perf/bench/futex.h @@ -18,6 +18,7 @@ struct bench_futex_parameters { bool fshared; bool mlockall; bool multi; /* lock-pi */ + bool pi; /* requeue-pi */ bool broadcast; /* requeue */ unsigned int runtime; /* seconds*/ unsigned int nthreads; @@ -90,7 +91,7 @@ futex_unlock_pi(u_int32_t *uaddr, int 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 +* @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, @@ -99,4 +100,38 @@ futex_cmp_requeue(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2, int nr_wak return futex(uaddr, FUTEX_CMP_REQUEUE, nr_wake, nr_requeue, uaddr2, val, opflags); } + +/** + * futex_wait_requeue_pi() - block on uaddr and prepare to requeue to uaddr2 + * @uaddr: non-PI futex source + * @uaddr2: PI futex target + * + * This is the first half of the requeue_pi mechanism. It shall always be + * paired with futex_cmp_requeue_pi(). + */ +static inline int +futex_wait_requeue_pi(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2, + struct timespec *timeout, int opflags) +{ + return futex(uaddr, FUTEX_WAIT_REQUEUE_PI, val, timeout, uaddr2, 0, + opflags); +} + +/** + * futex_cmp_requeue_pi() - requeue tasks from uaddr to uaddr2 + * @uaddr: non-PI futex source + * @uaddr2: PI futex target + * @nr_requeue: requeue up to this many tasks + * + * This is the second half of the requeue_pi mechanism. It shall always be + * paired with futex_wait_requeue_pi(). The first waker is always awoken. + */ +static inline int +futex_cmp_requeue_pi(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2, + int nr_requeue, int opflags) +{ + return futex(uaddr, FUTEX_CMP_REQUEUE_PI, 1, nr_requeue, uaddr2, + val, opflags); +} + #endif /* _FUTEX_H */ -- 2.7.4