I/OAT: set tcp_dma_copybreak to 256k for I/OAT ver.3
Maciej Sosnowski [Thu, 26 Feb 2009 10:05:17 +0000 (11:05 +0100)]
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@intel.com>
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/dma/ioatdma.h

index a3306d0..dcf8db5 100644 (file)
@@ -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
 }