[3.11.y.z extended stable] Patch "net: mvneta: increase the 64-bit rx/tx stats out of the hot path" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    net: mvneta: increase the 64-bit rx/tx stats out of the hot path

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 7f35a2e2f74f4d92983c3d914df0a428d2d33a7c Mon Sep 17 00:00:00 2001
From: willy tarreau <w at 1wt.eu>
Date: Thu, 16 Jan 2014 08:20:07 +0100
Subject: net: mvneta: increase the 64-bit rx/tx stats out of the hot path

commit dc4277dd41a80fd5f29a90412ea04bc3ba54fbf1 upstream.

Better count packets and bytes in the stack and on 32 bit then
accumulate them at the end for once. This saves two memory writes
and two memory barriers per packet. The incoming packet rate was
increased by 4.7% on the Openblocks AX3 thanks to this.

Cc: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Cc: Gregory CLEMENT <gregory.clement at free-electrons.com>
Reviewed-by: Eric Dumazet <edumazet at google.com>
Tested-by: Arnaud Ebalard <arno at natisbad.org>
Signed-off-by: Willy Tarreau <w at 1wt.eu>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Willy Tarreau <w at 1wt.eu>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/ethernet/marvell/mvneta.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index 1594c61d80de..64bf21be7ff9 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -1358,6 +1358,8 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,
 {
 	struct net_device *dev = pp->dev;
 	int rx_done, rx_filled;
+	u32 rcvd_pkts = 0;
+	u32 rcvd_bytes = 0;

 	/* Get number of received packets */
 	rx_done = mvneta_rxq_busy_desc_num_get(pp, rxq);
@@ -1395,10 +1397,8 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,

 		rx_bytes = rx_desc->data_size -
 			(ETH_FCS_LEN + MVNETA_MH_SIZE);
-		u64_stats_update_begin(&pp->rx_stats.syncp);
-		pp->rx_stats.packets++;
-		pp->rx_stats.bytes += rx_bytes;
-		u64_stats_update_end(&pp->rx_stats.syncp);
+		rcvd_pkts++;
+		rcvd_bytes += rx_bytes;

 		/* Linux processing */
 		skb_reserve(skb, MVNETA_MH_SIZE);
@@ -1419,6 +1419,13 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,
 		}
 	}

+	if (rcvd_pkts) {
+		u64_stats_update_begin(&pp->rx_stats.syncp);
+		pp->rx_stats.packets += rcvd_pkts;
+		pp->rx_stats.bytes   += rcvd_bytes;
+		u64_stats_update_end(&pp->rx_stats.syncp);
+	}
+
 	/* Update rxq management counters */
 	mvneta_rxq_desc_num_update(pp, rxq, rx_done, rx_filled);

--
1.9.1