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authorSangtae Ha <sangtae.ha@gmail.com>2011-03-14 10:52:18 +0300
committerDavid S. Miller <davem@davemloft.net>2011-03-15 01:54:42 +0300
commitb5ccd07337489fa9c9d32e0b628a2168b7953adf (patch)
tree4c0bd60c5500440e6a5bb7086d54dedfb8eed815 /net/ipv4/tcp_cubic.c
parent2b4636a5f8ca547000f6aba24ec1c58f31f4a91d (diff)
downloadlinux-b5ccd07337489fa9c9d32e0b628a2168b7953adf.tar.xz
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>
Diffstat (limited to 'net/ipv4/tcp_cubic.c')
-rw-r--r--net/ipv4/tcp_cubic.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 7172c129ff19..90d92dd4cf13 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -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;