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Commit 51b91468 authored by Michael Chan's avatar Michael Chan Committed by David S. Miller
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[TG3]: Minimize locking in TX path. 



This is similar to Eric Dumazet's tx_lock patch for tg3 but takes it
one step further to eliminate the tx_lock in the tx_completion path
when the tx queue is not stopped.

Signed-off-by: default avatarMichael Chan <mchan@broadcom.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 86d9f7f0

drivers/net/tg3.c

+13 −11
Original line number Diff line number Diff line
@@ -121,12 +121,9 @@ 
			           TG3_RX_RCB_RING_SIZE(tp))

#define TG3_TX_RING_BYTES	(sizeof(struct tg3_tx_buffer_desc) * \

				 TG3_TX_RING_SIZE)

#define TX_RING_GAP(TP)	\

	(TG3_TX_RING_SIZE - (TP)->tx_pending)

#define TX_BUFFS_AVAIL(TP)						\

	(((TP)->tx_cons <= (TP)->tx_prod) ?				\

	  (TP)->tx_cons + (TP)->tx_pending - (TP)->tx_prod :		\

	  (TP)->tx_cons - (TP)->tx_prod - TX_RING_GAP(TP))

	((TP)->tx_pending -						\

	 (((TP)->tx_prod - (TP)->tx_cons) & (TG3_TX_RING_SIZE - 1)))

#define NEXT_TX(N)		(((N) + 1) & (TG3_TX_RING_SIZE - 1))



#define RX_PKT_BUF_SZ		(1536 + tp->rx_offset + 64)
@@ -2880,9 +2877,13 @@ static void tg3_tx(struct tg3 *tp) 


	tp->tx_cons = sw_idx;



	if (unlikely(netif_queue_stopped(tp->dev))) {

		spin_lock(&tp->tx_lock);

		if (netif_queue_stopped(tp->dev) &&

		    (TX_BUFFS_AVAIL(tp) > TG3_TX_WAKEUP_THRESH))

			netif_wake_queue(tp->dev);

		spin_unlock(&tp->tx_lock);

	}

}



/* Returns size of skb allocated or < 0 on error.
@@ -3198,9 +3199,7 @@ static int tg3_poll(struct net_device *netdev, int *budget) 


	/* run TX completion thread */

	if (sblk->idx[0].tx_consumer != tp->tx_cons) {

		spin_lock(&tp->tx_lock);

		tg3_tx(tp);

		spin_unlock(&tp->tx_lock);

	}



	/* run RX thread, within the bounds set by NAPI.
@@ -3716,8 +3715,11 @@ static int tg3_start_xmit(struct sk_buff *skb, struct net_device *dev) 
	tw32_tx_mbox((MAILBOX_SNDHOST_PROD_IDX_0 + TG3_64BIT_REG_LOW), entry);



	tp->tx_prod = entry;

	if (TX_BUFFS_AVAIL(tp) <= (MAX_SKB_FRAGS + 1))

	if (TX_BUFFS_AVAIL(tp) <= (MAX_SKB_FRAGS + 1)) {

		netif_stop_queue(dev);

		if (TX_BUFFS_AVAIL(tp) > TG3_TX_WAKEUP_THRESH)

			netif_wake_queue(tp->dev);

	}



out_unlock:

    	mmiowb();