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Date: Mon, 9 Aug 2021 12:01:47 -0300 From: Arnaldo Carvalho de Melo <acme@...nel.org> To: Davidlohr Bueso <dave@...olabs.net> Cc: mingo@...hat.com, peterz@...radead.org, tglx@...utronix.de, linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de> Subject: Re: [PATCH 7/7] perf/bench-futex, requeue: Add --pi parameter Em Sun, Aug 08, 2021 at 09:33:01PM -0700, Davidlohr Bueso escreveu: > 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. Thanks, applied. - Arnaldo > Signed-off-by: Davidlohr Bueso <dbueso@...e.de> > --- > 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 e4892ba6864f..03a05814d45e 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 */ > @@ -53,6 +54,8 @@ 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() > }; > > @@ -86,14 +89,30 @@ 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; > + } > } > } > > @@ -170,9 +189,10 @@ 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); > @@ -182,7 +202,7 @@ 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 */ > @@ -200,13 +220,30 @@ 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); > @@ -216,16 +253,29 @@ 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 36f158650edf..f0ad6d988349 100644 > --- a/tools/perf/bench/futex.h > +++ b/tools/perf/bench/futex.h > @@ -21,6 +21,7 @@ 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; > @@ -93,7 +94,7 @@ 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, > @@ -102,4 +103,38 @@ 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 */ > -- > 2.26.2 > -- - Arnaldo
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