From 761965eab38d2cbc59c36e355c59609e3a04705a Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Sun, 4 Dec 2011 07:05:17 +0000
Subject: tcp: tcp_sendmsg() page recycling

If our TCP_PAGE(sk) is not shared (page_count() == 1), we can set page
offset to 0.

This permits better filling of the pages on small to medium tcp writes.

"tbench 16" results on my dev server (2x4x2 machine) :

Before : 3072 MB/s
After  : 3146 MB/s  (2.4 % gain)

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 45156be..a09fe25 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1009,7 +1009,12 @@ new_segment:
 				int merge = 0;
 				int i = skb_shinfo(skb)->nr_frags;
 				struct page *page = TCP_PAGE(sk);
-				int off = TCP_OFF(sk);
+				int off;
+
+				if (page && page_count(page) == 1)
+					TCP_OFF(sk) = 0;
+
+				off = TCP_OFF(sk);
 
 				if (skb_can_coalesce(skb, i, page, off) &&
 				    off != PAGE_SIZE) {
-- 
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