From: Thomas Graf <tgraf@redhat.com>
Date: Fri, 23 Jul 2010 15:33:13 -0400
Subject: [net] tcp: backport cubic update for net-2.6.22
Message-id: <20100723153313.GG14925@lsx.localdomain>
Patchwork-id: 27065
O-Subject: [RHEL5.6 PATCH 5/14] tcp: cubic update for net-2.6.22
Bugzilla: 612709
RH-Acked-by: Neil Horman <nhorman@redhat.com>
RH-Acked-by: David S. Miller <davem@redhat.com>

commit e1c3e7ab6de9711d2e0e9daf369c6638582eb7e7
Author: Stephen Hemminger <shemminger@linux-foundation.org>
Date:   Sat Mar 24 21:34:38 2007 -0700

    [TCP]: cubic update for net-2.6.22

    The following update received from Injong updates TCP cubic to the latest
    version. I am running more complete tests and will have results after 4/1.

    According to Injong: the new version improves on its scalability,
    fairness and stability.  So in all properties, we confirmed it shows better
    performance.

    NCSU results (for 2.6.18 and 2.6.20) available:
    	http://netsrv.csc.ncsu.edu/wiki/index.php/TCP_Testing

    This version is described in a new Internet draft for CUBIC.
    	http://www.ietf.org/internet-drafts/draft-rhee-tcp-cubic-00.txt

    Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Jarod Wilson <jarod@redhat.com>

diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 7ae00ae..7492234 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -1,5 +1,5 @@
 /*
- * TCP CUBIC: Binary Increase Congestion control for TCP v2.0
+ * TCP CUBIC: Binary Increase Congestion control for TCP v2.1
  *
  * This is from the implementation of CUBIC TCP in
  * Injong Rhee, Lisong Xu.
@@ -215,7 +215,9 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
 	if (ca->delay_min > 0) {
 		/* max increment = Smax * rtt / 0.1  */
 		min_cnt = (cwnd * HZ * 8)/(10 * max_increment * ca->delay_min);
-		if (ca->cnt < min_cnt)
+
+		/* use concave growth when the target is above the origin */
+		if (ca->cnt < min_cnt && t >= ca->bic_K)
 			ca->cnt = min_cnt;
 	}
 
@@ -401,4 +403,4 @@ module_exit(cubictcp_unregister);
 MODULE_AUTHOR("Sangtae Ha, Stephen Hemminger");
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("CUBIC TCP");
-MODULE_VERSION("2.0");
+MODULE_VERSION("2.1");