On Thu, Oct 31, 2013 at 06:28:33PM +0800, Jason Wang wrote:
> Commit 2613af0ed18a11d5c566a81f9a6510b73180660a (virtio_net: migrate mergeable
> rx buffers to page frag allocators) try to increase the payload/truesize for
> MTU-sized traffic. But this will introduce the extra overhead for GSO packets
> received because of the frag list. This commit tries to reduce this issue by
> coalesce the possible rx frags when possible during rx. Test result shows the
> about 15% improvement on full size GSO packet receiving (and even better than
> commit 2613af0ed18a11d5c566a81f9a6510b73180660a).
>
> Before this commit:
> ./netperf -H 192.168.100.4
> MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.100.4
> () port 0 AF_INET : demo
> Recv Send Send
> Socket Socket Message Elapsed
> Size Size Size Time Throughput
> bytes bytes bytes secs. 10^6bits/sec
>
> 87380 16384 16384 10.00 20303.87
>
> After this commit:
> ./netperf -H 192.168.100.4
> MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.100.4 () port 0 AF_INET : demo
> Recv Send Send
> Socket Socket Message Elapsed
> Size Size Size Time Throughput
> bytes bytes bytes secs. 10^6bits/sec
>
> 87380 16384 16384 10.00 23841.26
>
> Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Cc: Michael Dalton <mwdalton@xxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
Good idea.
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
> drivers/net/virtio_net.c | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 113ee93..4ff4f78 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -305,7 +305,7 @@ static int receive_mergeable(struct receive_queue *rq, struct sk_buff *head_skb)
> struct sk_buff *curr_skb = head_skb;
> char *buf;
> struct page *page;
> - int num_buf, len;
> + int num_buf, len, offset;
>
> num_buf = hdr->mhdr.num_buffers;
> while (--num_buf) {
> @@ -342,9 +342,15 @@ static int receive_mergeable(struct receive_queue *rq, struct sk_buff *head_skb)
> head_skb->truesize += MAX_PACKET_LEN;
> }
> page = virt_to_head_page(buf);
> - skb_add_rx_frag(curr_skb, num_skb_frags, page,
> - buf - (char *)page_address(page), len,
> - MAX_PACKET_LEN);
> + offset = buf - (char *)page_address(page);
> + if (skb_can_coalesce(curr_skb, num_skb_frags, page, offset)) {
> + skb_coalesce_rx_frag(curr_skb, num_skb_frags - 1,
> + offset, len, MAX_PACKET_LEN);
> + } else {
> + skb_add_rx_frag(curr_skb, num_skb_frags, page,
> + offset, len,
> + MAX_PACKET_LEN);
> + }
> --rq->num;
> }
> return 0;
> --
> 1.8.1.2
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