[ovs-dev] [PATCHv2] dpif-netdev: fix meter at high packet rate.

[William Tu]

When testing packet rate around 1Mpps with meter enabled, the frequency
of hitting meter action becomes much higher, around 30us each time.
As a result, the meter's calculation of 'uint32_t delta_t' becomes
always 0 and meter action has no effect.  This is due to the previous
commit 05f9e707e194 divides the delta by 1000, in order to convert to
msec granularity.  The patch fixes it updating the time when across
millisecond boundary.

Fixes: 05f9e707e194 ("dpif-netdev: Use microsecond granularity.")
Cc: Ilya Maximets <i.maximets at samsung.com>
Cc: Yi-Hung Wei <yihung.wei at gmail.com>
Signed-off-by: William Tu <u9012063 at gmail.com>
---
 lib/dpif-netdev.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index c20f875ee097..7a572df641f6 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -5549,7 +5549,7 @@ dp_netdev_run_meter(struct dp_netdev *dp, struct dp_packet_batch *packets_,
     memset(exceeded_rate, 0, cnt * sizeof *exceeded_rate);
 
     /* All packets will hit the meter at the same time. */
-    long_delta_t = (now - meter->used) / 1000; /* msec */
+    long_delta_t = now / 1000 - meter->used / 1000; /* msec */
 
     /* Make sure delta_t will not be too large, so that bucket will not
      * wrap around below. */
@@ -5557,7 +5557,7 @@ dp_netdev_run_meter(struct dp_netdev *dp, struct dp_packet_batch *packets_,
         ? meter->max_delta_t : (uint32_t)long_delta_t;
 
     /* Update meter stats. */
-    meter->used = now;
+    meter->used = delta_t > 0 ? now : meter->used;
     meter->packet_count += cnt;
     bytes = 0;
     DP_PACKET_BATCH_FOR_EACH (i, packet, packets_) {
-- 
2.7.4