[dpdk-stable] [PATCH 16.11 2/2] net/bonding: fix Rx slave fairness

[Chas Williams]

From: Chas Williams <chas3 at att.com>

[ upstream commit e1110e97764873de0af28e6fa11dcd9c170d4e53 ]

Some PMDs, especially ones with vector receives, require a minimum number
of receive buffers in order to receive any packets.  If the first slave
read leaves less than this number available, a read from the next slave
may return 0 implying that the slave doesn't have any packets which
results in skipping over that slave as the next active slave.

To fix this, implement round robin for the slaves during receive that
is only advanced to the next slave at the end of each receive burst.
This is also done to provide some additional fairness in processing in
other bonding RX burst routines as well.

Fixes: 2efb58cbab6e ("bond: new link bonding library")
Cc: stable at dpdk.org

Signed-off-by: Chas Williams <chas3 at att.com>
Acked-by: Luca Boccassi <bluca at debian.org>
Acked-by: Matan Azrad <matan at mellanox.com>
---
 drivers/net/bonding/rte_eth_bond_pmd.c | 30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/drivers/net/bonding/rte_eth_bond_pmd.c b/drivers/net/bonding/rte_eth_bond_pmd.c
index 15e893240..87a247de3 100644
--- a/drivers/net/bonding/rte_eth_bond_pmd.c
+++ b/drivers/net/bonding/rte_eth_bond_pmd.c
@@ -83,28 +83,34 @@ bond_ethdev_rx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 {
 	struct bond_dev_private *internals;
 
-	uint16_t num_rx_slave = 0;
 	uint16_t num_rx_total = 0;
-
+	uint16_t slave_count;
+	uint16_t active_slave;
 	int i;
 
 	/* Cast to structure, containing bonded device's port id and queue id */
 	struct bond_rx_queue *bd_rx_q = (struct bond_rx_queue *)queue;
-
 	internals = bd_rx_q->dev_private;
+	slave_count = internals->active_slave_count;
+	active_slave = internals->active_slave;
 
+	for (i = 0; i < slave_count && nb_pkts; i++) {
+		uint16_t num_rx_slave;
 
-	for (i = 0; i < internals->active_slave_count && nb_pkts; i++) {
 		/* Offset of pointer to *bufs increases as packets are received
 		 * from other slaves */
-		num_rx_slave = rte_eth_rx_burst(internals->active_slaves[i],
-				bd_rx_q->queue_id, bufs + num_rx_total, nb_pkts);
-		if (num_rx_slave) {
-			num_rx_total += num_rx_slave;
-			nb_pkts -= num_rx_slave;
-		}
+		num_rx_slave =
+			rte_eth_rx_burst(internals->active_slaves[active_slave],
+					 bd_rx_q->queue_id,
+					 bufs + num_rx_total, nb_pkts);
+		num_rx_total += num_rx_slave;
+		nb_pkts -= num_rx_slave;
+		if (++active_slave == slave_count)
+			active_slave = 0;
 	}
 
+	if (++internals->active_slave == slave_count)
+		internals->active_slave = 0;
 	return num_rx_total;
 }
 
@@ -212,7 +218,9 @@ bond_ethdev_rx_burst_8023ad(void *queue, struct rte_mbuf **bufs,
 			idx = 0;
 	}
 
-	internals->active_slave = idx;
+	if (++internals->active_slave == slave_count)
+		internals->active_slave = 0;
+
 	return num_rx_total;
 }
 
-- 
2.14.4