bonding: Add tlb_dynamic_lb parameter for tlb mode

The aggresive load balancing causes packet re-ordering as active
flows are moved from a slave to another within the group. Sometime
this aggresive lb is not necessary if the preference is for less
re-ordering. This parameter if used with value "0" disables
this dynamic flow shuffling minimizing packet re-ordering. Of course
the side effect is that it has to live with the static load balancing
that the hashing distribution provides. This impact is less severe if
the correct xmit-hashing-policy is used for the tlb setup.

The default value of the parameter is set to "1" mimicing the earlier
behavior.

Ran the netperf test with 200 stream for 1 min between two hosts with
4x1G trunk (xmit-lb mode with xmit-policy L3+4) before and after these
changes. Following was the command used for those 200 instances -

    netperf -t TCP_RR -l 60 -s 5 -H <host> -- -r81920,81920

Transactions per second:
    Before change: 1,367.11
    After  change: 1,470.65

Change-Id: Ie3f75c77282cf602e83a6e833c6eb164e72a0990
Signed-off-by: Mahesh Bandewar <maheshb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 4 deletions

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index 153232ed4b3f..70de039dad2e 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -1356,7 +1356,8 @@ static int bond_do_alb_xmit(struct sk_buff *skb, struct bonding *bond,
         if (!tx_slave) {
                 /* unbalanced or unassigned, send through primary */
                 tx_slave = rcu_dereference(bond->curr_active_slave);
-                bond_info->unbalanced_load += skb->len;
+                if (bond->params.tlb_dynamic_lb)
+                        bond_info->unbalanced_load += skb->len;
         }
 
         if (tx_slave && SLAVE_IS_OK(tx_slave)) {
@@ -1369,7 +1370,7 @@ static int bond_do_alb_xmit(struct sk_buff *skb, struct bonding *bond,
                 goto out;
         }
 
-        if (tx_slave) {
+        if (tx_slave && bond->params.tlb_dynamic_lb) {
                 _lock_tx_hashtbl(bond);
                 __tlb_clear_slave(bond, tx_slave, 0);
                 _unlock_tx_hashtbl(bond);
@@ -1399,11 +1400,21 @@ int bond_tlb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
                     /* In case of IPX, it will falback to L2 hash */
                 case htons(ETH_P_IPV6):
                         hash_index = bond_xmit_hash(bond, skb);
-                        tx_slave = tlb_choose_channel(bond, hash_index & 0xFF, skb->len);
+                        if (bond->params.tlb_dynamic_lb) {
+                                tx_slave = tlb_choose_channel(bond,
+                                                              hash_index & 0xFF,
+                                                              skb->len);
+                        } else {
+                                struct list_head *iter;
+                                int idx = hash_index % bond->slave_cnt;
+
+                                bond_for_each_slave_rcu(bond, tx_slave, iter)
+                                        if (--idx < 0)
+                                                break;
+                        }
                         break;
                 }
         }
-
         return bond_do_alb_xmit(skb, bond, tx_slave);
 }