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virtio-net: coalesce rx frags when possible during rx 

Commit 2613af0ed1 (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
before commit 2613af0ed1).

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@rustcorp.com.au>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Michael Dalton <mwdalton@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
wifi-calibration
Jason Wang 2013-11-01 14:07:48 +08:00 committed by David S. Miller
parent f8e617e100
commit ba27524103
1 changed files with 11 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/net/virtio_net.c
View File

@ -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 +342,16 @@ 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)) {
put_page(page);
skb_coalesce_rx_frag(curr_skb, num_skb_frags - 1,
len, MAX_PACKET_LEN);
} else {
skb_add_rx_frag(curr_skb, num_skb_frags, page,
offset, len,
MAX_PACKET_LEN);
}
--rq->num;
}
return 0;