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: NMaciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: NShannon Nelson <shannon.nelson@intel.com>
Acked-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/dma/ioatdma.h

@@ -135,12 +135,14 @@ static inline void ioat_set_tcp_copy_break(struct ioatdma_device *dev)
 	#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
 }