Re: Major network performance regression in 3.7

Eric Dumazet
2013-01-06T01:51:26Z

On Sat, 2013-01-05 at 17:40 -0800, Eric Dumazet wrote:
> On Sun, 2013-01-06 at 02:30 +0100, Willy Tarreau wrote:
>
> > Ah interesting because these were some of the mm patches that I had
> > tried to revert.
>
> Hmm, or we should fix __skb_splice_bits()
>
> I'll send a patch.
>

Could you try the following ?

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 3ab989b..c5246be 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1768,14 +1768,15 @@ static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
struct splice_pipe_desc *spd, struct sock *sk)
{
int seg;
+ struct page *page = virt_to_page(skb->data);
+ unsigned int poff = skb->data - (unsigned char *)page_address(page);

/* map the linear part :
* If skb->head_frag is set, this 'linear' part is backed by a
* fragment, and if the head is not shared with any clones then
* we can avoid a copy since we own the head portion of this page.
*/
- if (__splice_segment(virt_to_page(skb->data),
- (unsigned long) skb->data & (PAGE_SIZE - 1),
+ if (__splice_segment(page, poff,
skb_headlen(skb),
offset, len, skb, spd,
skb_head_is_locked(skb),