netdev - [PATCH 4/5] mv643xx_eth: avoid reading ->byte

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <20080914171449.GF28798@xi.wantstofly.org>
Date:	Sun, 14 Sep 2008 19:14:49 +0200
From:	Lennert Buytenhek <buytenh@...tstofly.org>
To:	netdev@...r.kernel.org
Cc:	Dale Farnsworth <dale@...nsworth.org>,
	Ashish Karkare <akarkare@...vell.com>,
	Nicolas Pitre <nico@....org>
Subject: [PATCH 4/5] mv643xx_eth: avoid reading ->byte_cnt twice during receive processing

Currently, the receive processing reads ->byte_cnt twice (once to
update interface statistics and once to properly size the data area
of the received skb), but since receive descriptors live in uncached
memory, caching this value in a local variable saves one uncached
access, and increases routing performance a tiny little bit more.

Signed-off-by: Lennert Buytenhek <buytenh@...vell.com>
---
 drivers/net/mv643xx_eth.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mv643xx_eth.c b/drivers/net/mv643xx_eth.c
index 4fbd62e..6564be1 100644
--- a/drivers/net/mv643xx_eth.c
+++ b/drivers/net/mv643xx_eth.c
@@ -477,6 +477,7 @@ static int rxq_process(struct rx_queue *rxq, int budget)
 		struct rx_desc *rx_desc;
 		unsigned int cmd_sts;
 		struct sk_buff *skb;
+		u16 byte_cnt;
 
 		rx_desc = &rxq->rx_desc_area[rxq->rx_curr_desc];
 
@@ -499,6 +500,8 @@ static int rxq_process(struct rx_queue *rxq, int budget)
 
 		mp->work_rx_refill |= 1 << rxq->index;
 
+		byte_cnt = rx_desc->byte_cnt;
+
 		/*
 		 * Update statistics.
 		 *
@@ -508,7 +511,7 @@ static int rxq_process(struct rx_queue *rxq, int budget)
 		 * byte CRC at the end of the packet (which we do count).
 		 */
 		stats->rx_packets++;
-		stats->rx_bytes += rx_desc->byte_cnt - 2;
+		stats->rx_bytes += byte_cnt - 2;
 
 		/*
 		 * In case we received a packet without first / last bits
@@ -537,7 +540,7 @@ static int rxq_process(struct rx_queue *rxq, int budget)
 			 * The -4 is for the CRC in the trailer of the
 			 * received packet
 			 */
-			skb_put(skb, rx_desc->byte_cnt - 2 - 4);
+			skb_put(skb, byte_cnt - 2 - 4);
 
 			if (cmd_sts & LAYER_4_CHECKSUM_OK) {
 				skb->ip_summed = CHECKSUM_UNNECESSARY;
-- 
1.5.6.4
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html