net: tx scalability works : trans_start

struct net_device trans_start field is a hot spot on SMP and high performance
devices, particularly multi queues ones, because every transmitter dirties
it. Is main use is tx watchdog and bonding alive checks.

But as most devices dont use NETIF_F_LLTX, we have to lock
a netdev_queue before calling their ndo_start_xmit(). So it makes
sense to move trans_start from net_device to netdev_queue. Its update
will occur on a already present (and in exclusive state) cache line, for
free.

We can do this transition smoothly. An old driver continue to
update dev->trans_start, while an updated one updates txq->trans_start.

Further patches could also put tx_bytes/tx_packets counters in 
netdev_queue to avoid dirtying dev->stats (vlan device comes to mind)

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 815191d..30b9ea6 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2795,7 +2795,7 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
 	 */
 	bond_for_each_slave(bond, slave, i) {
 		if (slave->link != BOND_LINK_UP) {
-			if (time_before_eq(jiffies, slave->dev->trans_start + delta_in_ticks) &&
+			if (time_before_eq(jiffies, dev_trans_start(slave->dev) + delta_in_ticks) &&
 			    time_before_eq(jiffies, slave->dev->last_rx + delta_in_ticks)) {
 
 				slave->link  = BOND_LINK_UP;
@@ -2827,7 +2827,7 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
 			 * when the source ip is 0, so don't take the link down
 			 * if we don't know our ip yet
 			 */
-			if (time_after_eq(jiffies, slave->dev->trans_start + 2*delta_in_ticks) ||
+			if (time_after_eq(jiffies, dev_trans_start(slave->dev) + 2*delta_in_ticks) ||
 			    (time_after_eq(jiffies, slave->dev->last_rx + 2*delta_in_ticks))) {
 
 				slave->link  = BOND_LINK_DOWN;
@@ -2938,7 +2938,7 @@ static int bond_ab_arp_inspect(struct bonding *bond, int delta_in_ticks)
 		 *    the bond has an IP address)
 		 */
 		if ((slave->state == BOND_STATE_ACTIVE) &&
-		    (time_after_eq(jiffies, slave->dev->trans_start +
+		    (time_after_eq(jiffies, dev_trans_start(slave->dev) +
 				    2 * delta_in_ticks) ||
 		      (time_after_eq(jiffies, slave_last_rx(bond, slave)
 				     + 2 * delta_in_ticks)))) {
@@ -2982,7 +2982,7 @@ static void bond_ab_arp_commit(struct bonding *bond, int delta_in_ticks)
 			write_lock_bh(&bond->curr_slave_lock);
 
 			if (!bond->curr_active_slave &&
-			    time_before_eq(jiffies, slave->dev->trans_start +
+			    time_before_eq(jiffies, dev_trans_start(slave->dev) +
 					   delta_in_ticks)) {
 				slave->link = BOND_LINK_UP;
 				bond_change_active_slave(bond, slave);