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Commit 7d0105b5 authored by Malcolm Crossley's avatar Malcolm Crossley Committed by David S. Miller
Browse files

xen-netfront: request Tx response events more often 



Trying to batch Tx response events results in poor performance because
this delays freeing the transmitted skbs.

Instead use the standard RING_FINAL_CHECK_FOR_RESPONSES() macro to be
notified once the next Tx response is placed on the ring.

Signed-off-by: default avatarMalcolm Crossley <malcolm.crossley@citrix.com>
Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3b89624a

drivers/net/xen-netfront.c

+3 −12
Original line number Diff line number Diff line
@@ -364,6 +364,7 @@ static void xennet_tx_buf_gc(struct netfront_queue *queue) 
	RING_IDX cons, prod;

	unsigned short id;

	struct sk_buff *skb;

	bool more_to_do;



	BUG_ON(!netif_carrier_ok(queue->info->netdev));
@@ -398,18 +399,8 @@ static void xennet_tx_buf_gc(struct netfront_queue *queue) 


		queue->tx.rsp_cons = prod;



		/*

		 * Set a new event, then check for race with update of tx_cons.

		 * Note that it is essential to schedule a callback, no matter

		 * how few buffers are pending. Even if there is space in the

		 * transmit ring, higher layers may be blocked because too much

		 * data is outstanding: in such cases notification from Xen is

		 * likely to be the only kick that we'll get.

		 */

		queue->tx.sring->rsp_event =

			prod + ((queue->tx.sring->req_prod - prod) >> 1) + 1;

		mb();		/* update shared area */

	} while ((cons == prod) && (prod != queue->tx.sring->rsp_prod));

		RING_FINAL_CHECK_FOR_RESPONSES(&queue->tx, more_to_do);

	} while (more_to_do);



	xennet_maybe_wake_tx(queue);

}