At 11:49 AM 15/07/2002 +0200, Andrea Arcangeli wrote:
> > my test app uses pthreads (one thread per disk-worker) and
> > pthread_cond_wait in the master task to wait for all workers to finish.
> > i'll switch the app to use clone() and sys_futex instead.
>
>unless you call pthread routines during the workload, pthreads cannot be
>the reason for a slowdown.
the test app does:
(parent)
for (i=0; i < num_devices; i++) {
err = pthread_create(&(device[i]->thread), NULL, (void
*)run_tests, (void *) i);
..
}
/* wait for all threads to exit */
while (active_threads != 0) {
pthread_mutex_lock(&sync_thread_mutex);
gettimeofday(&now, NULL);
timeout.tv_sec = now.tv_sec + 5;
timeout.tv_nsec = now.tv_usec * 1000;
retcode = 0;
while ((active_threads != 0) && (retcode != ETIMEDOUT)) {
retcode =
pthread_cond_timedwait(&sync_thread_cond, &sync_thread_mutex, &timeout);
}
if (retcode == ETIMEDOUT) {
print_status_update();
}
pthread_mutex_unlock(&sync_thread_mutex);
}
(each worker, when it finishes)
pthread_mutex_lock(&sync_thread_mutex);
active_threads--;
pthread_cond_broadcast(&sync_thread_cond);
pthread_mutex_unlock(&sync_thread_mutex);
pthread_exit(0);
no idea what the pthread_cond_timedwait does under the covers, but i bet
its bad..
>BTW, Lincol, I still have a pending answer for you, about the mmap
>slowdown, that's because of reduced readahead mostly, you can tune it
>with page-cluster sysctl, it's not only because of the expensive page
>faults that mmap I/O implies. I've some revolutionary idea about
>replacing readahead, not that it matters for your workload that is
>reading physically contigous though.
i only added the mmap() for interests-sake; the intent of my benchmarking
was less-so to stress linux, more-so to stress some storage-networking
plumbing (iSCSI & FC stuff), but its been an interesting series of
experiments nontheless.
cheers,
lincoln.
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This archive was generated by hypermail 2b29 : Mon Jul 15 2002 - 22:00:30 EST