From: Stephen Hemminger <shemminger@linux-foundation.org>
To: "Julian Shao Liu" <shaoliu@uiuc.edu>,
"David S. Miller" <davem@davemloft.net>,
Herbert Xu <herbert@gondor.apana.org.au>
Cc: "'Lachlan Andrew'" <lachlan.andrew@gmail.com>,
<shaoliu@Princeton.EDU>, "'Douglas Leith'" <doug.leith@nuim.ie>,
"'Robert Shorten'" <robert.shorten@nuim.ie>,
netdev@vger.kernel.org
Subject: [PATCH] tcp-illinois: incorrect beta usage
Date: Wed, 28 Nov 2007 15:47:25 -0800 [thread overview]
Message-ID: <20071128154725.29af2852@freepuppy.rosehill> (raw)
In-Reply-To: <001001c83063$9adbc9d0$d5897e82@csp.uiuc.edu>
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>
--- a/net/ipv4/tcp_illinois.c 2007-08-18 07:50:15.000000000 -0700
+++ b/net/ipv4/tcp_illinois.c 2007-11-28 15:39:04.000000000 -0800
@@ -298,7 +298,7 @@ static u32 tcp_illinois_ssthresh(struct
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);
}
next parent reply other threads:[~2007-11-28 23:50 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <aa7d2c6d0711261023m3d2dd850o76a8f44aef022f39@mail.gmail.com>
[not found] ` <001001c83063$9adbc9d0$d5897e82@csp.uiuc.edu>
2007-11-28 23:47 ` Stephen Hemminger [this message]
2007-11-29 0:25 ` [PATCH] tcp-illinois: incorrect beta usage Lachlan Andrew
2007-11-29 0:43 ` Stephen Hemminger
2007-11-29 5:26 ` Shao Liu
2007-12-03 22:52 ` [RFC] TCP illinois max rtt aging Stephen Hemminger
2007-12-03 23:06 ` Lachlan Andrew
2007-12-03 23:59 ` Shao Liu
2007-12-04 0:32 ` Stephen Hemminger
2007-12-04 1:23 ` Lachlan Andrew
2007-12-04 8:37 ` Ilpo Järvinen
2007-12-07 3:27 ` Lachlan Andrew
2007-12-07 11:05 ` Ilpo Järvinen
2007-12-07 12:41 ` David Miller
2007-12-07 13:05 ` Ilpo Järvinen
2007-12-07 18:27 ` Ilpo Järvinen
2007-12-08 1:32 ` David Miller
2007-12-11 11:59 ` [RFC PATCH net-2.6.25 uncompilable] [TCP]: Avoid breaking GSOed skbs when SACKed one-by-one (Was: Re: [RFC] TCP illinois max rtt aging) Ilpo Järvinen
2007-12-11 12:32 ` [RFC PATCH net-2.6.25 uncompilable] [TCP]: Avoid breaking GSOed skbs when SACKed one-by-one David Miller
2007-12-12 0:14 ` Lachlan Andrew
2007-12-12 15:11 ` David Miller
2007-12-12 23:35 ` Lachlan Andrew
2007-12-12 23:38 ` David Miller
2007-12-13 0:00 ` Stephen Hemminger
2007-12-15 9:51 ` SACK scoreboard (Was: Re: [RFC PATCH net-2.6.25 uncompilable] [TCP]: Avoid breaking GSOed skbs when SACKed one-by-one) Ilpo Järvinen
2008-01-08 7:36 ` SACK scoreboard David Miller
2008-01-08 12:12 ` Ilpo Järvinen
2008-01-09 7:58 ` David Miller
2008-01-08 16:51 ` John Heffner
2008-01-08 22:44 ` David Miller
2008-01-09 1:34 ` Lachlan Andrew
2008-01-09 6:35 ` David Miller
2008-01-09 2:25 ` Andi Kleen
2008-01-09 4:27 ` John Heffner
2008-01-09 6:41 ` David Miller
2008-01-09 14:56 ` John Heffner
2008-01-09 18:14 ` SANGTAE HA
2008-01-09 18:23 ` John Heffner
2008-01-09 12:55 ` Ilpo Järvinen
2008-01-09 6:39 ` David Miller
2008-01-09 7:03 ` Andi Kleen
2008-01-09 7:16 ` David Miller
2008-01-09 9:47 ` Evgeniy Polyakov
2008-01-09 14:02 ` Andi Kleen
2007-11-29 14:12 ` [PATCH] tcp-illinois: incorrect beta usage Herbert Xu
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