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Commit 547c890c authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
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virtio-net: avoid unnecessary sg initialzation 



Usually an skb does not have up to MAX_SKB_FRAGS frags. So no need to
initialize the unuse part of sg. This patch initialize the sg based on
the real number it will used:

- during xmit, it could be inferred from nr_frags and can_push.
- for small receive buffer, it will also be 2.

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5e0aa597

drivers/net/virtio_net.c

+2 −2
Original line number Diff line number Diff line
@@ -540,7 +540,7 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq, 
	skb_put(skb, GOOD_PACKET_LEN);



	hdr = skb_vnet_hdr(skb);

	sg_init_table(rq->sg, MAX_SKB_FRAGS + 2);

	sg_init_table(rq->sg, 2);

	sg_set_buf(rq->sg, hdr, vi->hdr_len);

	skb_to_sgvec(skb, rq->sg + 1, 0, skb->len);
@@ -893,7 +893,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb) 
	if (vi->mergeable_rx_bufs)

		hdr->num_buffers = 0;



	sg_init_table(sq->sg, MAX_SKB_FRAGS + 2);

	sg_init_table(sq->sg, skb_shinfo(skb)->nr_frags + (can_push ? 1 : 2));

	if (can_push) {

		__skb_push(skb, hdr_len);

		num_sg = skb_to_sgvec(skb, sq->sg, 0, skb->len);