From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: The AI parameter of tcp_highspeed.c (in 2.6.18) Date: Fri, 2 Jun 2006 12:05:07 -0700 Message-ID: <20060602120507.7e1206d8@dxpl.pdx.osdl.net> References: <7335583a0605292112l1f5a6ec3x4b1c1e4ae45688f5@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org Return-path: Received: from smtp.osdl.org ([65.172.181.4]:37504 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1751433AbWFBTFO (ORCPT ); Fri, 2 Jun 2006 15:05:14 -0400 To: "Xiaoliang (David) Wei" , John Heffner In-Reply-To: <7335583a0605292112l1f5a6ec3x4b1c1e4ae45688f5@mail.gmail.com> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Went backed and looked at the RFC. The problem was just a simple translation of table to C array (0 based). Added this to the TCP testing repository. Subject: [PATCH] Problem observed by Xiaoliang (David) Wei: When snd_cwnd is smaller than 38 and the connection is in congestion avoidance phase (snd_cwnd > snd_ssthresh), the snd_cwnd seems to stop growing. The additive increase was confused because C array's are 0 based. Signed-off-by: Stephen Hemminger --- net/ipv4/tcp_highspeed.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) 121685b7b61c8faeb87e6c6f0c346b0fe1c46fd2 diff --git a/net/ipv4/tcp_highspeed.c b/net/ipv4/tcp_highspeed.c index b72fa55..ba7c63c 100644 --- a/net/ipv4/tcp_highspeed.c +++ b/net/ipv4/tcp_highspeed.c @@ -135,7 +135,8 @@ static void hstcp_cong_avoid(struct sock /* Do additive increase */ if (tp->snd_cwnd < tp->snd_cwnd_clamp) { - tp->snd_cwnd_cnt += ca->ai; + /* cwnd = cwnd + a(w) / cwnd */ + tp->snd_cwnd_cnt += ca->ai + 1; if (tp->snd_cwnd_cnt >= tp->snd_cwnd) { tp->snd_cwnd_cnt -= tp->snd_cwnd; tp->snd_cwnd++; -- 1.3.3