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| author | Stephen Hemminger <shemminger@linux-foundation.org> | 2007-11-30 01:10:55 +1100 |
|---|---|---|
| committer | Herbert Xu <herbert@gondor.apana.org.au> | 2007-11-30 01:10:55 +1100 |
| commit | a357dde9df33f28611e6a3d4f88265e39bcc8880 (patch) | |
| tree | 181c8b1508a84ca30d32c779a508bb475fb96077 /net/ipv4 | |
| parent | 5e5234ff17ef98932688116025b30958bd28a940 (diff) | |
| download | linux-stable-a357dde9df33f28611e6a3d4f88265e39bcc8880.tar.gz linux-stable-a357dde9df33f28611e6a3d4f88265e39bcc8880.tar.bz2 linux-stable-a357dde9df33f28611e6a3d4f88265e39bcc8880.zip | |
[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')
| -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 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); } |