netdev - [PATCH] ibmveth: Increase default copybreak limits to 2k

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Message-ID: <20101021143753.GA5567@linux.vnet.ibm.com>
Date:	Thu, 21 Oct 2010 09:37:53 -0500
From:	Robert Jennings <rcj@...ux.vnet.ibm.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: [PATCH] ibmveth: Increase default copybreak limits to 2k

Increase the copybreak limits for rx and tx from 128 bytes
to 2048 bytes. These limits were added by commits
8d86c61ae41d9068fd5e5cc01a4abd53c4fe3ab5 and
c08cc3ccebd46dce44d13a8ce81d249e687eeb8a to make use of a
bounce buffer for packets below 128 bytes.  This avoids
tearing down and creating a TCE entry.

Performance testing shows that this default limit can be
increased from 128 to 2048 for both rx and tx copybreak.
This resulted in ~10% throughput increase for for packets
that fit this limit without affecting performance for larger
packets.

Signed-off-by: Robert Jennings <rcj@...ux.vnet.ibm.com>
---
 drivers/net/ibmveth.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ibmveth.c b/drivers/net/ibmveth.c
index c454b45..20b7a98 100644
--- a/drivers/net/ibmveth.c
+++ b/drivers/net/ibmveth.c
@@ -65,12 +65,12 @@ MODULE_DESCRIPTION("IBM Power Virtual Ethernet Driver");
 MODULE_LICENSE("GPL");
 MODULE_VERSION(ibmveth_driver_version);
 
-static unsigned int tx_copybreak __read_mostly = 128;
+static unsigned int tx_copybreak __read_mostly = 2048;
 module_param(tx_copybreak, uint, 0644);
 MODULE_PARM_DESC(tx_copybreak,
 	"Maximum size of packet that is copied to a new buffer on transmit");
 
-static unsigned int rx_copybreak __read_mostly = 128;
+static unsigned int rx_copybreak __read_mostly = 2048;
 module_param(rx_copybreak, uint, 0644);
 MODULE_PARM_DESC(rx_copybreak,
 	"Maximum size of packet that is copied to a new buffer on receive");
-- 
1.7.0.4

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