Re: [PATCH net-next] tcp: better use ooo_last_skb in tcp_data_queue_ofo()

[David Miller]

From: Eric Dumazet 
Date: Fri, 09 Sep 2016 14:22:45 -0700

> From: Eric Dumazet 
> 
> Willem noticed that we could avoid an rbtree lookup if the
> the attempt to coalesce incoming skb to the last skb failed
> for some reason.
> 
> Since most ooo additions are at the tail, this is definitely
> worth adding a test and fast path.
> 
> Suggested-by: Willem de Bruijn 
> Signed-off-by: Eric Dumazet 

Applied, thanks.

[PATCH net-next] tcp: better use ooo_last_skb in tcp_data_queue_ofo()

[Eric Dumazet]

From: Eric Dumazet 

Willem noticed that we could avoid an rbtree lookup if the
the attempt to coalesce incoming skb to the last skb failed
for some reason.

Since most ooo additions are at the tail, this is definitely
worth adding a test and fast path.

Suggested-by: Willem de Bruijn 
Signed-off-by: Eric Dumazet 
Cc: Yaogong Wang 
Cc: Yuchung Cheng 
Cc: Neal Cardwell 
Cc: Ilpo Järvinen 
---
 net/ipv4/tcp_input.c |8 +++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a5934c4c8cd4..2e26f3eb0293 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4461,6 +4461,12 @@ coalesce_done:
skb = NULL;
goto add_sack;
}
+   /* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */
+   if (!before(seq, TCP_SKB_CB(tp->ooo_last_skb)->end_seq)) {
+   parent = >ooo_last_skb->rbnode;
+   p = >rb_right;
+   goto insert;
+   }
 
/* Find place to insert this segment. Handle overlaps on the way. */
parent = NULL;
@@ -4503,7 +4509,7 @@ coalesce_done:
}
p = >rb_right;
}
-
+insert:
/* Insert segment into RB tree. */
rb_link_node(>rbnode, parent, p);
rb_insert_color(>rbnode, >out_of_order_queue);