Patchwork [4/4] USBNET: ax88179_178a: enable tso if host supports sg dma

login
register
mail settings
Submitter Eric Dumazet
Date Aug. 1, 2013, 5:04 a.m.
Message ID <1375333461.10515.133.camel@edumazet-glaptop>
Download mbox | patch
Permalink /patch/263918/
State RFC
Delegated to: David Miller
Headers show

Comments

Eric Dumazet - Aug. 1, 2013, 5:04 a.m.
On Thu, 2013-08-01 at 12:41 +0800, Ming Lei wrote:

> From my trace result, lots of linear SKBs are cloned or header-cloned, so
> it needs skb copy too.
> 
> Is it normal in xmit path to see cloned SKBs for driver? If not, I can add check
> to avoid allocation of 8 bytes header for non-cloned skb.

Existing code is not very friendly and very complex.

Sure TCP stack does a clone for every skb from socket write queue,
but header should be available for pushing 8 bytes.

The !skb_cloned(skb) test should be removed if the memmove() is not
needed.

Could you try following patch ?

 drivers/net/usb/ax88179_178a.c |   21 ++++-----------------
 1 file changed, 4 insertions(+), 17 deletions(-)



--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Ming Lei - Aug. 1, 2013, 8:10 a.m.
On Thu, Aug 1, 2013 at 1:04 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Thu, 2013-08-01 at 12:41 +0800, Ming Lei wrote:
>
>> From my trace result, lots of linear SKBs are cloned or header-cloned, so
>> it needs skb copy too.
>>
>> Is it normal in xmit path to see cloned SKBs for driver? If not, I can add check
>> to avoid allocation of 8 bytes header for non-cloned skb.
>
> Existing code is not very friendly and very complex.
>
> Sure TCP stack does a clone for every skb from socket write queue,
> but header should be available for pushing 8 bytes.
>
> The !skb_cloned(skb) test should be removed if the memmove() is not
> needed.
>
> Could you try following patch ?

Tested-by: Ming Lei <ming.lei@canonical.com>

This patch does work, and it will make the patch 4/4 become very
simple, :-)

I will rewrite this one against your patch.

Thanks,
--
Ming Lei
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Eric Dumazet - Aug. 1, 2013, 1:21 p.m.
On Thu, 2013-08-01 at 16:10 +0800, Ming Lei wrote:
> On Thu, Aug 1, 2013 at 1:04 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > On Thu, 2013-08-01 at 12:41 +0800, Ming Lei wrote:
> >
> >> From my trace result, lots of linear SKBs are cloned or header-cloned, so
> >> it needs skb copy too.
> >>
> >> Is it normal in xmit path to see cloned SKBs for driver? If not, I can add check
> >> to avoid allocation of 8 bytes header for non-cloned skb.
> >
> > Existing code is not very friendly and very complex.
> >
> > Sure TCP stack does a clone for every skb from socket write queue,
> > but header should be available for pushing 8 bytes.
> >
> > The !skb_cloned(skb) test should be removed if the memmove() is not
> > needed.
> >
> > Could you try following patch ?
> 
> Tested-by: Ming Lei <ming.lei@canonical.com>
> 
> This patch does work, and it will make the patch 4/4 become very
> simple, :-)
> 
> I will rewrite this one against your patch.

OK I'll post an official patch then. I presume you got performance
increase, since we no longer do a copy of the TCP packets.



--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/drivers/net/usb/ax88179_178a.c b/drivers/net/usb/ax88179_178a.c
index 2bc87e3..e2120d6 100644
--- a/drivers/net/usb/ax88179_178a.c
+++ b/drivers/net/usb/ax88179_178a.c
@@ -1166,31 +1166,18 @@  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);