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Commit 64f2525c authored by Andrew Lunn's avatar Andrew Lunn Committed by Jeff Kirsher
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igb: Only DMA sync frame length 



On some platforms, syncing a buffer for DMA is expensive. Rather than
sync the whole 2K receive buffer, only synchronise the length of the
frame, which will typically be the MTU, or a much smaller TCP ACK.

For an IMX6Q, this gives around 6% increased TCP receive performance,
which is cache operations bound and reduces CPU load for TCP transmit.

Signed-off-by: default avatarAndrew Lunn <andrew@lunn.ch>
Tested-by: default avatarAaron Brown <aaron.f.brown@intel.com>
Signed-off-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
parent 581e0c7d

drivers/net/ethernet/intel/igb/igb_main.c

+4 −3
Original line number Diff line number Diff line
@@ -6856,12 +6856,12 @@ static bool igb_can_reuse_rx_page(struct igb_rx_buffer *rx_buffer, 
 **/

static bool igb_add_rx_frag(struct igb_ring *rx_ring,

			    struct igb_rx_buffer *rx_buffer,

			    unsigned int size,

			    union e1000_adv_rx_desc *rx_desc,

			    struct sk_buff *skb)

{

	struct page *page = rx_buffer->page;

	unsigned char *va = page_address(page) + rx_buffer->page_offset;

	unsigned int size = le16_to_cpu(rx_desc->wb.upper.length);

#if (PAGE_SIZE < 8192)

	unsigned int truesize = IGB_RX_BUFSZ;

#else
@@ -6913,6 +6913,7 @@ static struct sk_buff *igb_fetch_rx_buffer(struct igb_ring *rx_ring, 
					   union e1000_adv_rx_desc *rx_desc,

					   struct sk_buff *skb)

{

	unsigned int size = le16_to_cpu(rx_desc->wb.upper.length);

	struct igb_rx_buffer *rx_buffer;

	struct page *page;
@@ -6948,11 +6949,11 @@ static struct sk_buff *igb_fetch_rx_buffer(struct igb_ring *rx_ring, 
	dma_sync_single_range_for_cpu(rx_ring->dev,

				      rx_buffer->dma,

				      rx_buffer->page_offset,

				      IGB_RX_BUFSZ,

				      size,

				      DMA_FROM_DEVICE);



	/* pull page into skb */

	if (igb_add_rx_frag(rx_ring, rx_buffer, rx_desc, skb)) {

	if (igb_add_rx_frag(rx_ring, rx_buffer, size, rx_desc, skb)) {

		/* hand second half of page back to the ring */

		igb_reuse_rx_page(rx_ring, rx_buffer);

	} else {