From: Stephen Hemminger <shemminger@vyatta•com>
To: "David S. Miller" <davem@davemloft•net>
Cc: netdev@vger•kernel.org, Sangtae Ha <sangtae.ha@gmail•com>
Subject: [PATCH 7/7] tcp_cubic: fix low utilization of CUBIC with HyStart
Date: Mon, 14 Mar 2011 10:52:18 -0700 [thread overview]
Message-ID: <20110314175439.844558845@vyatta.com> (raw)
In-Reply-To: 20110314175211.788224699@vyatta.com
[-- Attachment #1: tcp-cubic-initial-growth.patch --]
[-- Type: text/plain, Size: 1077 bytes --]
From: Sangtae Ha <sangtae.ha@gmail•com>
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>
---
net/ipv4/tcp_cubic.c | 9 +++++++++
1 files changed, 9 insertions(+), 0 deletions(-)
--- a/net/ipv4/tcp_cubic.c 2011-03-14 08:32:46.347993869 -0700
+++ b/net/ipv4/tcp_cubic.c 2011-03-14 10:57:00.846549449 -0700
@@ -270,6 +270,13 @@ static inline void bictcp_update(struct
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;
next prev parent reply other threads:[~2011-03-14 18:02 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-14 17:52 [PATCH 0/7] TCP CUBIC Hystart fixes Stephen Hemminger
2011-03-14 17:52 ` [PATCH 1/7] tcp: fix RTT for quick packets in congestion control Stephen Hemminger
2011-03-14 17:52 ` [PATCH 2/7] tcp_cubic: fix comparison of jiffies Stephen Hemminger
2011-03-14 17:52 ` [PATCH 3/7] tcp_cubic: make ack train delta value a parameter Stephen Hemminger
2011-03-14 17:52 ` [PATCH 4/7] tcp_cubic: fix clock dependency Stephen Hemminger
2011-03-14 18:51 ` Eric Dumazet
2011-03-14 21:21 ` Stephen Hemminger
2011-03-14 21:37 ` Eric Dumazet
2011-03-14 17:52 ` [PATCH 5/7] tcp_cubic: enable high resolution ack time if needed Stephen Hemminger
2011-03-14 17:52 ` [PATCH 6/7] tcp_cubic: make the delay threshold of HyStart less sensitive Stephen Hemminger
2011-03-14 17:52 ` Stephen Hemminger [this message]
2011-03-14 22:58 ` [PATCH 0/7] TCP CUBIC Hystart fixes David Miller
2011-03-22 11:34 ` Lucas Nussbaum
2011-03-22 11:35 ` Lucas Nussbaum
2011-03-22 12:05 ` David Miller
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