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ax88179_178a: avoid copy of tx tcp packets 

ax88179_tx_fixup() has quite complex code trying to push 8 bytes
of control data (len/mss), but fails to do it properly for TCP packets,
incurring an extra copy and point of memory allocation failure.

Lets use the simple and approved way.

dev->needed_headroom being 8, all frames should have 8 bytes of
headroom, so the extra copy should be unlikely anyway.

This patch should improve performance for TCP xmits.

Reported-by: Ming Lei <ming.lei@canonical.com>
Tested-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2013-08-01 06:49:52 -07:00 committed by David S. Miller
parent 0e76a3a587
commit f27070158d
1 changed files with 4 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
drivers/net/usb/ax88179_178a.c
View File

@ -1169,31 +1169,18 @@ ax88179_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
int frame_size = dev->maxpacket;
int mss = skb_shinfo(skb)->gso_size;
int headroom;
int tailroom;
tx_hdr1 = skb->len;
tx_hdr2 = mss;
if (((skb->len + 8) % frame_size) == 0)
tx_hdr2 |= 0x80008000; /* Enable padding */
headroom = skb_headroom(skb);
tailroom = skb_tailroom(skb);
headroom = skb_headroom(skb) - 8;
if (!skb_header_cloned(skb) &&
!skb_cloned(skb) &&
(headroom + tailroom) >= 8) {
if (headroom < 8) {
skb->data = memmove(skb->head + 8, skb->data, skb->len);
skb_set_tail_pointer(skb, skb->len);
}
} else {
struct sk_buff *skb2;
skb2 = skb_copy_expand(skb, 8, 0, flags);
if ((skb_header_cloned(skb) || headroom < 0) &&
pskb_expand_head(skb, headroom < 0 ? 8 : 0, 0, GFP_ATOMIC)) {
dev_kfree_skb_any(skb);
skb = skb2;
if (!skb)
return NULL;
return NULL;
}
skb_push(skb, 4);