From patchwork Mon Mar 14 17:52:18 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: stephen hemminger X-Patchwork-Id: 86791 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 33D0DB6F7A for ; Tue, 15 Mar 2011 05:02:29 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757162Ab1CNSCX (ORCPT ); Mon, 14 Mar 2011 14:02:23 -0400 Received: from suva.vyatta.com ([76.74.103.44]:58253 "EHLO suva.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757057Ab1CNSCE (ORCPT ); Mon, 14 Mar 2011 14:02:04 -0400 Received: from suva.vyatta.com (suva [127.0.0.1]) by suva.vyatta.com (8.13.7/8.13.7) with ESMTP id p2EI1OdD014865; Mon, 14 Mar 2011 11:01:24 -0700 Received: (from shemminger@localhost) by suva.vyatta.com (8.13.7/8.13.7/Submit) id p2EI1OMH014864; Mon, 14 Mar 2011 11:01:24 -0700 Message-Id: <20110314175439.844558845@vyatta.com> User-Agent: quilt/0.48-1 Date: Mon, 14 Mar 2011 10:52:18 -0700 From: Stephen Hemminger To: "David S. Miller" Cc: netdev@vger.kernel.org, Sangtae Ha Subject: [PATCH 7/7] tcp_cubic: fix low utilization of CUBIC with HyStart References: <20110314175211.788224699@vyatta.com> Content-Disposition: inline; filename=tcp-cubic-initial-growth.patch Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Sangtae Ha HyStart sets the initial exit point of slow start. Suppose that HyStart exits at 0.5BDP in a BDP network and no history exists. If the BDP of a network is large, CUBIC's initial cwnd growth may be too conservative to utilize the link. CUBIC increases the cwnd 20% per RTT in this case. Signed-off-by: Sangtae Ha Acked-by: Stephen Hemminger --- net/ipv4/tcp_cubic.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html --- a/net/ipv4/tcp_cubic.c 2011-03-14 08:32:46.347993869 -0700 +++ b/net/ipv4/tcp_cubic.c 2011-03-14 10:57:00.846549449 -0700 @@ -270,6 +270,13 @@ static inline void bictcp_update(struct ca->cnt = 100 * cwnd; /* very small increment*/ } + /* + * The initial growth of cubic function may be too conservative + * when the available bandwidth is still unknown. + */ + if (ca->loss_cwnd == 0 && ca->cnt > 20) + ca->cnt = 20; /* increase cwnd 5% per RTT */ + /* TCP Friendly */ if (tcp_friendliness) { u32 scale = beta_scale;