Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761701AbXLMGqf (ORCPT ); Thu, 13 Dec 2007 01:46:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759733AbXLMGiE (ORCPT ); Thu, 13 Dec 2007 01:38:04 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:56551 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759720AbXLMGiB (ORCPT ); Thu, 13 Dec 2007 01:38:01 -0500 Date: Wed, 12 Dec 2007 22:35:09 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org, davem@davemloft.net Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , Chuck Ebbert , Domenico Andreoli , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Stephen Hemminger , Herbert Xu Subject: [patch 25/36] TCP: illinois: Incorrect beta usage Message-ID: <20071213063509.GZ25301@kroah.com> References: <20071213062511.265908583@mini.kroah.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline; filename="tcp-illinois-incorrect-beta-usage.patch" In-Reply-To: <20071213063308.GA25301@kroah.com> User-Agent: Mutt/1.5.16 (2007-06-09) X-Bad-Reply: References and In-Reply-To but no 'Re:' in Subject. Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1589 Lines: 49 2.6.22-stable review patch. If anyone has any objections, please let us know. ------------------ From: Stephen Hemminger [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 Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp_illinois.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/ipv4/tcp_illinois.c +++ b/net/ipv4/tcp_illinois.c @@ -300,7 +300,7 @@ 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); } -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/