pktgen: remove ndelay() call

Daniel Turull reported inaccuracies in pktgen when using low packet
rates, because we call ndelay(val) with values bigger than 20000.

Instead of calling ndelay() for delays < 100us, we can instead loop
calling ktime_now() only.

Reported-by: Daniel Turull <daniel.turull@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 6bbf008..0001c24 100644 (file)
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -2145,9 +2145,12 @@ static void spin(struct pktgen_dev *pkt_dev, ktime_t spin_until)
        }
 
        start_time = ktime_now();
-       if (remaining < 100000)
-               ndelay(remaining);      /* really small just spin */
-       else {
+       if (remaining < 100000) {
+               /* for small delays (<100us), just loop until limit is reached */
+               do {
+                       end_time = ktime_now();
+               } while (ktime_lt(end_time, spin_until));
+       } else {
                /* see do_nanosleep */
                hrtimer_init_sleeper(&t, current);
                do {
@@ -2162,8 +2165,8 @@ static void spin(struct pktgen_dev *pkt_dev, ktime_t spin_until)
                        hrtimer_cancel(&t.timer);
                } while (t.task && pkt_dev->running && !signal_pending(current));
                __set_current_state(TASK_RUNNING);
+               end_time = ktime_now();
        }
-       end_time = ktime_now();
 
        pkt_dev->idle_acc += ktime_to_ns(ktime_sub(end_time, start_time));
        pkt_dev->next_tx = ktime_add_ns(spin_until, pkt_dev->delay);