Commit aaf27254 authored by Maciej Fijalkowski's avatar Maciej Fijalkowski Committed by Jeff Kirsher
Browse files

ice: add build_skb() support 



Driver is now prepared for building the skb around the existing Rx
buffer, so introduce the ice_build_skb responsible for it. Make use of
XDP's data_meta as well.

I've observed around 30% less CPU consumption with build_skb Rx path, in
comparison to legacy Rx. What stands behind such result is the avoidance
of flow_dissector (which we were diving into via eth_get_headlen) and no
memcpy calls.

Signed-off-by: default avatarMaciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: default avatarAndrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
parent 59bb0808

drivers/net/ethernet/intel/ice/ice_txrx.c

+59 −1
Original line number Diff line number Diff line
@@ -790,6 +790,60 @@ ice_get_rx_buf(struct ice_ring *rx_ring, struct sk_buff **skb, 
	return rx_buf;

}



/**

 * ice_build_skb - Build skb around an existing buffer

 * @rx_ring: Rx descriptor ring to transact packets on

 * @rx_buf: Rx buffer to pull data from

 * @xdp: xdp_buff pointing to the data

 *

 * This function builds an skb around an existing Rx buffer, taking care

 * to set up the skb correctly and avoid any memcpy overhead.

 */

static struct sk_buff *

ice_build_skb(struct ice_ring *rx_ring, struct ice_rx_buf *rx_buf,

	      struct xdp_buff *xdp)

{

	unsigned int metasize = xdp->data - xdp->data_meta;

#if (PAGE_SIZE < 8192)

	unsigned int truesize = ice_rx_pg_size(rx_ring) / 2;

#else

	unsigned int truesize = SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) +

				SKB_DATA_ALIGN(xdp->data_end -

					       xdp->data_hard_start);

#endif

	struct sk_buff *skb;



	/* Prefetch first cache line of first page. If xdp->data_meta

	 * is unused, this points exactly as xdp->data, otherwise we

	 * likely have a consumer accessing first few bytes of meta

	 * data, and then actual data.

	 */

	prefetch(xdp->data_meta);

#if L1_CACHE_BYTES < 128

	prefetch((void *)(xdp->data + L1_CACHE_BYTES));

#endif

	/* build an skb around the page buffer */

	skb = build_skb(xdp->data_hard_start, truesize);

	if (unlikely(!skb))

		return NULL;



	/* must to record Rx queue, otherwise OS features such as

	 * symmetric queue won't work

	 */

	skb_record_rx_queue(skb, rx_ring->q_index);



	/* update pointers within the skb to store the data */

	skb_reserve(skb, xdp->data - xdp->data_hard_start);

	__skb_put(skb, xdp->data_end - xdp->data);

	if (metasize)

		skb_metadata_set(skb, metasize);



	/* buffer is used by skb, update page_offset */

	ice_rx_buf_adjust_pg_offset(rx_buf, truesize);



	return skb;

}



/**

 * ice_construct_skb - Allocate skb and populate it

 * @rx_ring: Rx descriptor ring to transact packets on
@@ -996,12 +1050,14 @@ static int ice_clean_rx_irq(struct ice_ring *rx_ring, int budget) 
		if (!size) {

			xdp.data = NULL;

			xdp.data_end = NULL;

			xdp.data_hard_start = NULL;

			xdp.data_meta = NULL;

			goto construct_skb;

		}



		xdp.data = page_address(rx_buf->page) + rx_buf->page_offset;

		xdp.data_hard_start = xdp.data - ice_rx_offset(rx_ring);

		xdp_set_data_meta_invalid(&xdp);

		xdp.data_meta = xdp.data;

		xdp.data_end = xdp.data + size;



		rcu_read_lock();
@@ -1038,6 +1094,8 @@ static int ice_clean_rx_irq(struct ice_ring *rx_ring, int budget) 
construct_skb:

		if (skb)

			ice_add_rx_frag(rx_ring, rx_buf, skb, size);

		else if (ice_ring_uses_build_skb(rx_ring))

			skb = ice_build_skb(rx_ring, rx_buf, &xdp);

		else

			skb = ice_construct_skb(rx_ring, rx_buf, &xdp);

CRA Git | Maintained and supported by SUSTech CRA and CCSE