netdev - [PATCH net-next 4/6] net: mvneta: prefetch next rx descriptor instead of current one

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Date:	Sun, 12 Jan 2014 12:24:06 +0100
From:	Willy Tarreau <w@....eu>
To:	davem@...emloft.net
Cc:	netdev@...r.kernel.org, Willy Tarreau <w@....eu>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Gregory CLEMENT <gregory.clement@...e-electrons.com>
Subject: [PATCH net-next 4/6] net: mvneta: prefetch next rx descriptor instead of current one

Currently, the mvneta driver tries to prefetch the current Rx
descriptor during read. Tests have shown that prefetching the
next one instead increases general performance by about 1% on
HTTP traffic.

Cc: Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Cc: Gregory CLEMENT <gregory.clement@...e-electrons.com>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/net/ethernet/marvell/mvneta.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index aa3a4f7..c7b37e0 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -611,6 +611,7 @@ mvneta_rxq_next_desc_get(struct mvneta_rx_queue *rxq)
 	int rx_desc = rxq->next_desc_to_proc;
 
 	rxq->next_desc_to_proc = MVNETA_QUEUE_NEXT_DESC(rxq, rx_desc);
+	prefetch(rxq->descs + rxq->next_desc_to_proc);
 	return rxq->descs + rx_desc;
 }
 
@@ -1442,7 +1443,6 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,
 		u32 rx_status;
 		int rx_bytes, err;
 
-		prefetch(rx_desc);
 		rx_done++;
 		rx_filled++;
 		rx_status = rx_desc->status;
-- 
1.7.12.2.21.g234cd45.dirty

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