From: Jason Wang Date: Thu, 27 Aug 2015 06:53:06 +0000 (+0800) Subject: virtio-net: avoid unnecessary sg initialzation X-Git-Tag: firefly_0821_release~176^2~1159^2~64 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=547c890cfd26010e01b3faf98f29ca9b2252c8d8;p=firefly-linux-kernel-4.4.55.git 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 Signed-off-by: Jason Wang Signed-off-by: David S. Miller --- diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 9b950f2db836..d8838dedb7a4 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -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);