linux-kernel - [PATCH 5/7] I/OAT: set tcp_dma_copybreak to 256k for I/OAT ver.3

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Message-ID: <20090226100515.3615.70407.stgit@linux.site>
Date:	Thu, 26 Feb 2009 11:05:17 +0100
From:	Maciej Sosnowski <maciej.sosnowski@...el.com>
To:	dan.j.williams@...el.com
Cc:	snakebyte@....de, shannon.nelson@...el.com,
	jeffrey.t.krisher@...el.com, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: [PATCH 5/7] I/OAT: set tcp_dma_copybreak to 256k for I/OAT ver.3

Upcoming server platforms from Intel based on the Nehalem performance
have significantly improved CPU based copy performance.
However, the DMA engine can still be effective at higher I/O sizes
for TCP traffic and at this time copybreak
should be set to 256k for TCP traffic only.

Signed-off-by: Maciej Sosnowski <maciej.sosnowski@...el.com>
Signed-off-by: Shannon Nelson <shannon.nelson@...el.com>
Acked-by: Jeff Kirsher <jeffrey.t.krisher@...el.com>
---

 drivers/dma/ioatdma.h |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/dma/ioatdma.h b/drivers/dma/ioatdma.h
index a3306d0..dcf8db5 100644
--- a/drivers/dma/ioatdma.h
+++ b/drivers/dma/ioatdma.h
@@ -135,12 +135,14 @@ static inline void ioat_set_tcp_copy_bre
 	#ifdef CONFIG_NET_DMA
 	switch (dev->version) {
 	case IOAT_VER_1_2:
-	case IOAT_VER_3_0:
 		sysctl_tcp_dma_copybreak = 4096;
 		break;
 	case IOAT_VER_2_0:
 		sysctl_tcp_dma_copybreak = 2048;
 		break;
+	case IOAT_VER_3_0:
+		sysctl_tcp_dma_copybreak = 262144;
+		break;
 	}
 	#endif
 }

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