Add gtod_cpu option for pinning gettimeofday() to a single CPU

[fio.git] / fio.c

diff --git a/fio.c b/fio.c
index 5a87ae4b000fe377ad9970fa7971f725c287c020..a58effcf3394816b20d04937de81f77f1a0c179f 100644 (file)
--- a/fio.c
+++ b/fio.c
@@ -55,6 +55,7 @@ static struct fio_mutex *startup_mutex;
 static volatile int fio_abort;
 static int exit_value;
 static struct itimerval itimer;
+static pthread_t gtod_thread;
 
 struct io_log *agg_io_log[2];
 
@@ -964,6 +965,18 @@ static void *thread_main(void *data)
                goto err;
        }
 
+       if (td->o.gtod_cpu) {
+               if (fio_getaffinity(td->pid, &td->o.cpumask) == -1) {
+                       td_verror(td, errno, "cpu_get_affinity");
+                       goto err;
+               }
+               fio_cpu_clear(&td->o.cpumask, td->o.gtod_cpu);
+               if (fio_setaffinity(td) == -1) {
+                       td_verror(td, errno, "cpu_set_affinity");
+                       goto err;
+               }
+       }
+
        if (td->ioprio_set) {
                if (ioprio_set(IOPRIO_WHO_PROCESS, 0, td->ioprio) == -1) {
                        td_verror(td, errno, "ioprio_set");
@@ -1229,6 +1242,39 @@ reaped:
                terminate_threads(TERMINATE_ALL);
 }
 
+static void *gtod_thread_main(void *data)
+{
+       fio_mutex_up(startup_mutex);
+
+       /*
+        * As long as we have jobs around, update the clock. It would be nice
+        * to have some way of NOT hammering that CPU with gettimeofday(),
+        * but I'm not sure what to use outside of a simple CPU nop to relax
+        * it - we don't want to lose precision.
+        */
+       while (threads) {
+               fio_gtod_update();
+               nop;
+       }
+
+       return NULL;
+}
+
+static int fio_start_gtod_thread(void)
+{
+       if (pthread_create(&gtod_thread, NULL, gtod_thread_main, NULL)) {
+               perror("Can't create gtod thread");
+               return 1;
+       }
+       if (pthread_detach(gtod_thread) < 0) {
+               perror("Can't detatch gtod thread");
+               return 1;
+       }
+
+       fio_mutex_down(startup_mutex);
+       return 0;
+}
+
 /*
  * Main function for kicking off and reaping jobs, as needed.
  */
@@ -1241,6 +1287,9 @@ static void run_threads(void)
        if (fio_pin_memory())
                return;
 
+       if (fio_gtod_offload && fio_start_gtod_thread())
+               return;
+
        if (!terse_output) {
                printf("Starting ");
                if (nr_thread)