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| author | Stephen Hemminger <shemminger@linux-foundation.org> | 2007-12-11 09:39:37 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2007-12-14 10:31:59 -0800 |
| commit | 11af41fed1cfedd6b501e726f8b361a1420b7d5e (patch) | |
| tree | bfd581b1435e885f46aae286981ee94a90ea8d33 | |
| parent | ebfc4b6b2b23f051b2651fc72efde160b3ff02ec (diff) | |
| download | lwn-11af41fed1cfedd6b501e726f8b361a1420b7d5e.tar.gz lwn-11af41fed1cfedd6b501e726f8b361a1420b7d5e.zip | |
TCP: illinois: Incorrect beta usage
[TCP] illinois: Incorrect beta usage
[ Upstream commit: a357dde9df33f28611e6a3d4f88265e39bcc8880 ]
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | net/ipv4/tcp_illinois.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c index b2b2256d3b84..31dd8c54e137 100644 --- a/net/ipv4/tcp_illinois.c +++ b/net/ipv4/tcp_illinois.c @@ -300,7 +300,7 @@ 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); } |