path: root/net/ipv4/tcp_illinois.c
diff options
authorStephen Hemminger <shemminger@linux-foundation.org>2007-11-30 01:10:55 +1100
committerHerbert Xu <herbert@gondor.apana.org.au>2007-11-30 01:10:55 +1100
commita357dde9df33f28611e6a3d4f88265e39bcc8880 (patch)
tree181c8b1508a84ca30d32c779a508bb475fb96077 /net/ipv4/tcp_illinois.c
parent[IPSEC]: Fix uninitialised dst warning in __xfrm_lookup (diff)
[TCP] illinois: Incorrect beta usage
Lachlan Andrew observed that my TCP-Illinois implementation uses the beta value incorrectly: The parameter beta in the paper specifies the amount to decrease *by*: that is, on loss, W <- W - beta*W but in tcp_illinois_ssthresh() uses beta as the amount to decrease *to*: W <- beta*W This bug makes the Linux TCP-Illinois get less-aggressive on uncongested network, hurting performance. Note: since the base beta value is .5, it has no impact on a congested network. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'net/ipv4/tcp_illinois.c')
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c
index 64f1cbaf96e8..5aa5f5496d6d 100644
--- a/net/ipv4/tcp_illinois.c
+++ b/net/ipv4/tcp_illinois.c
@@ -298,7 +298,7 @@ static u32 tcp_illinois_ssthresh(struct sock *sk)
struct illinois *ca = inet_csk_ca(sk);
/* Multiplicative decrease */
- return max((tp->snd_cwnd * ca->beta) >> BETA_SHIFT, 2U);
+ return max(tp->snd_cwnd - ((tp->snd_cwnd * ca->beta) >> BETA_SHIFT), 2U);