[dpdk-dev] [PATCH 1/2] net/ixgbe: calculate the correct number of received packets in bulk alloc function

[Jianbo Liu]

To get better performance, Rx bulk alloc recv function will scan 8 descriptors
in one time, but the statuses are not consistent on ARM platform because
the memory allocated for Rx descriptors is cacheable hugepages.
This patch is to calculate the number of received packets by scanning DD bit
sequentially, and stops when meeting the first packet with DD bit unset.

Signed-off-by: Jianbo Liu <jianbo.liu at linaro.org>
---
 drivers/net/ixgbe/ixgbe_rxtx.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ixgbe/ixgbe_rxtx.c b/drivers/net/ixgbe/ixgbe_rxtx.c
index b2d9f45..2866bdb 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx.c
@@ -1402,17 +1402,21 @@ ixgbe_rx_scan_hw_ring(struct ixgbe_rx_queue *rxq)
 	for (i = 0; i < RTE_PMD_IXGBE_RX_MAX_BURST;
 	     i += LOOK_AHEAD, rxdp += LOOK_AHEAD, rxep += LOOK_AHEAD) {
 		/* Read desc statuses backwards to avoid race condition */
-		for (j = LOOK_AHEAD-1; j >= 0; --j)
+		for (j = LOOK_AHEAD - 1; j >= 0; --j) {
 			s[j] = rte_le_to_cpu_32(rxdp[j].wb.upper.status_error);
-
-		for (j = LOOK_AHEAD - 1; j >= 0; --j)
 			pkt_info[j] = rte_le_to_cpu_32(rxdp[j].wb.lower.
 						       lo_dword.data);
+		}
+
+		rte_smp_rmb();
 
 		/* Compute how many status bits were set */
 		nb_dd = 0;
 		for (j = 0; j < LOOK_AHEAD; ++j)
-			nb_dd += s[j] & IXGBE_RXDADV_STAT_DD;
+			if (s[j] & IXGBE_RXDADV_STAT_DD)
+				++nb_dd;
+			else
+				break;
 
 		nb_rx += nb_dd;
 
-- 
2.4.11