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Commit 92b9ccd3 authored by Rafał Miłecki's avatar Rafał Miłecki Committed by David S. Miller
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bgmac: pass received packet to the netif instead of copying it 



Copying whole packets with skb_copy_from_linear_data_offset is a pretty
bad idea. CPU was spending time in __copy_user_common and network
performance was lower. With the new solution iperf-measured speed
increased from 116Mb/s to 134Mb/s.

Signed-off-by: default avatarRafał Miłecki <zajec5@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3af390e2

drivers/net/ethernet/broadcom/bgmac.c

+39 −27
Original line number Diff line number Diff line
@@ -315,7 +315,6 @@ static int bgmac_dma_rx_read(struct bgmac *bgmac, struct bgmac_dma_ring *ring, 
		struct device *dma_dev = bgmac->core->dma_dev;

		struct bgmac_slot_info *slot = &ring->slots[ring->start];

		struct sk_buff *skb = slot->skb;

		struct sk_buff *new_skb;

		struct bgmac_rx_header *rx;

		u16 len, flags;
@@ -328,39 +327,52 @@ static int bgmac_dma_rx_read(struct bgmac *bgmac, struct bgmac_dma_ring *ring, 
		len = le16_to_cpu(rx->len);

		flags = le16_to_cpu(rx->flags);



		do {

			dma_addr_t old_dma_addr = slot->dma_addr;

			int err;



			/* Check for poison and drop or pass the packet */

			if (len == 0xdead && flags == 0xbeef) {

				bgmac_err(bgmac, "Found poisoned packet at slot %d, DMA issue!\n",

					  ring->start);

		} else {

				dma_sync_single_for_device(dma_dev,

							   slot->dma_addr,

							   BGMAC_RX_BUF_SIZE,

							   DMA_FROM_DEVICE);

				break;

			}



			/* Omit CRC. */

			len -= ETH_FCS_LEN;



			new_skb = netdev_alloc_skb_ip_align(bgmac->net_dev, len);

			if (new_skb) {

				skb_put(new_skb, len);

				skb_copy_from_linear_data_offset(skb, BGMAC_RX_FRAME_OFFSET,

								 new_skb->data,

								 len);

				skb_checksum_none_assert(skb);

				new_skb->protocol =

					eth_type_trans(new_skb, bgmac->net_dev);

				netif_receive_skb(new_skb);

				handled++;

			} else {

				bgmac->net_dev->stats.rx_dropped++;

				bgmac_err(bgmac, "Allocation of skb for copying packet failed!\n");

			}



			/* Prepare new skb as replacement */

			err = bgmac_dma_rx_skb_for_slot(bgmac, slot);

			if (err) {

				/* Poison the old skb */

				rx->len = cpu_to_le16(0xdead);

				rx->flags = cpu_to_le16(0xbeef);



				dma_sync_single_for_device(dma_dev,

							   slot->dma_addr,

							   BGMAC_RX_BUF_SIZE,

							   DMA_FROM_DEVICE);

				break;

			}

			bgmac_dma_rx_setup_desc(bgmac, ring, ring->start);



		/* Make it back accessible to the hardware */

		dma_sync_single_for_device(dma_dev, slot->dma_addr,

			/* Unmap old skb, we'll pass it to the netfif */

			dma_unmap_single(dma_dev, old_dma_addr,

					 BGMAC_RX_BUF_SIZE, DMA_FROM_DEVICE);



			skb_put(skb, BGMAC_RX_FRAME_OFFSET + len);

			skb_pull(skb, BGMAC_RX_FRAME_OFFSET);



			skb_checksum_none_assert(skb);

			skb->protocol = eth_type_trans(skb, bgmac->net_dev);

			netif_receive_skb(skb);

			handled++;

		} while (0);



		if (++ring->start >= BGMAC_RX_RING_SLOTS)

			ring->start = 0;