From: Eric Dumazet <edumazet@google.com>
Date: Thu, 11 Jun 2015 16:15:18 +0000 (-0700)
Subject: tcp: fill shinfo->gso_size at last moment
X-Git-Tag: omap-for-v4.2/fixes-rc1^2~134^2~76^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f69ad292cfd13aa7ee00847320c6bb9ba2154e87;p=pandora-kernel.git

tcp: fill shinfo->gso_size at last moment

In commit cd7d8498c9a5 ("tcp: change tcp_skb_pcount() location") we stored
gso_segs in a temporary cache hot location.

This patch does the same for gso_size.

This allows to save 2 cache line misses in tcp xmit path for
the last packet that is considered but not sent because of
various conditions (cwnd, tso defer, receiver window, TSQ...)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 978cebedd3fc..950cfecaad3c 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -730,11 +730,14 @@ struct tcp_skb_cb {
 		/* Note : tcp_tw_isn is used in input path only
 		 *	  (isn chosen by tcp_timewait_state_process())
 		 *
-		 * 	  tcp_gso_segs is used in write queue only,
-		 *	  cf tcp_skb_pcount()
+		 * 	  tcp_gso_segs/size are used in write queue only,
+		 *	  cf tcp_skb_pcount()/tcp_skb_mss()
 		 */
 		__u32		tcp_tw_isn;
-		__u32		tcp_gso_segs;
+		struct {
+			u16	tcp_gso_segs;
+			u16	tcp_gso_size;
+		};
 	};
 	__u8		tcp_flags;	/* TCP header flags. (tcp[13])	*/
 
@@ -790,10 +793,10 @@ static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
 	TCP_SKB_CB(skb)->tcp_gso_segs += segs;
 }
 
-/* This is valid iff tcp_skb_pcount() > 1. */
+/* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
 static inline int tcp_skb_mss(const struct sk_buff *skb)
 {
-	return skb_shinfo(skb)->gso_size;
+	return TCP_SKB_CB(skb)->tcp_gso_size;
 }
 
 /* Events passed to congestion control interface */
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