netdev - [PATCH 7/14] tcp: Optimise len/mss comparison

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Message-Id: <E1M9B5u-0001SI-Jj@gondolin.me.apana.org.au>
Date:	Wed, 27 May 2009 14:50:26 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: [PATCH 7/14] tcp: Optimise len/mss comparison

tcp: Optimise len/mss comparison

Instead of checking len > mss || len == 0, we can accomplish
both by checking (len - 1) > mss using the unsigned wraparound.
At nearly a million times a second, this might just help.

Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
---

 net/ipv4/tcp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 313960e..68342d4 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2566,7 +2566,7 @@ found:

 	mss = skb_shinfo(p)->gso_size;

-	flush |= (len > mss) | !len;
+	flush |= (len - 1) >= mss;
 	flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);

 	if (flush || skb_gro_receive(head, skb)) {
--
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