From: James Yang <[email protected]> The waker threads' processor affinity is not specified, so the result has run-to-run variability as the scheduler decides on which CPUs they are to run. So we add a -W/--affine-wakers flag to stripe the affinity of the waker threads across the online CPUs instead of having the scheduler place them.
Cc: Kim Phillips <[email protected]> Signed-off-by: James Yang <[email protected]> Signed-off-by: Davidlohr Bueso <[email protected]> --- tools/perf/bench/futex-wake-parallel.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/tools/perf/bench/futex-wake-parallel.c b/tools/perf/bench/futex-wake-parallel.c index 979e303e4797..c04e207ea37c 100644 --- a/tools/perf/bench/futex-wake-parallel.c +++ b/tools/perf/bench/futex-wake-parallel.c @@ -39,6 +39,7 @@ static u_int32_t futex = 0; static pthread_t *blocked_worker; static bool done = false, silent = false, fshared = false; +static bool affine_wakers = false; static unsigned int nblocked_threads = 0, nwaking_threads = 0; static pthread_mutex_t thread_lock; static pthread_cond_t thread_parent, thread_worker; @@ -51,6 +52,7 @@ static const struct option options[] = { 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_BOOLEAN( 'W', "affine-wakers", &affine_wakers, "Stripe affinity of waker threads across CPUs"), OPT_END() }; @@ -78,7 +80,8 @@ static void *waking_workerfn(void *arg) return NULL; } -static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr) +static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr, + struct cpu_map *cpu) { unsigned int i; @@ -91,6 +94,17 @@ static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr) * as it will affect the order to acquire the hb spinlock. * For now let the scheduler decide. */ + if (affine_wakers) { + cpu_set_t cpuset; + CPU_ZERO(&cpuset); + CPU_SET(cpu->map[(i + 1) % cpu->nr], &cpuset); + + if (pthread_attr_setaffinity_np(&thread_attr, + sizeof(cpu_set_t), + &cpuset)) + err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); + } + if (pthread_create(&td[i].worker, &thread_attr, waking_workerfn, (void *)&td[i])) err(EXIT_FAILURE, "pthread_create"); @@ -276,7 +290,7 @@ int bench_futex_wake_parallel(int argc, const char **argv) usleep(100000); /* Ok, all threads are patiently blocked, start waking folks up */ - wakeup_threads(waking_worker, thread_attr); + wakeup_threads(waking_worker, thread_attr, cpu); for (i = 0; i < nblocked_threads; i++) { ret = pthread_join(blocked_worker[i], NULL); -- 2.13.6
