Commit b5ccd073 authored Mar 14, 2011 by Sangtae Ha Committed by David S. Miller Mar 14, 2011

tcp_cubic: fix low utilization of CUBIC with HyStart



HyStart sets the initial exit point of slow start.
Suppose that HyStart exits at 0.5BDP in a BDP network and no history exists.
If the BDP of a network is large, CUBIC's initial cwnd growth may be
too conservative to utilize the link.
CUBIC increases the cwnd 20% per RTT in this case.

Signed-off-by: Sangtae Ha <sangtae.ha@gmail.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 2b4636a5

net/ipv4/tcp_cubic.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -270,6 +270,13 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
		ca->cnt = 100 * cwnd; /* very small increment*/
		}

		/*
		* The initial growth of cubic function may be too conservative
		* when the available bandwidth is still unknown.
		*/
		if (ca->loss_cwnd == 0 && ca->cnt > 20)
		ca->cnt = 20; /* increase cwnd 5% per RTT */

		/* TCP Friendly */
		if (tcp_friendliness) {
		u32 scale = beta_scale;

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