Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756889AbXJNBD6 (ORCPT ); Sat, 13 Oct 2007 21:03:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753972AbXJNBDu (ORCPT ); Sat, 13 Oct 2007 21:03:50 -0400 Received: from userg501.nifty.com ([202.248.238.81]:17298 "EHLO userg501.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753867AbXJNBDt (ORCPT ); Sat, 13 Oct 2007 21:03:49 -0400 DomainKey-Signature: a=rsa-sha1; s=userg501; d=nifty.com; c=nofws; q=dns; h=date:from:to:cc:subject:message-id:in-reply-to:references: x-mailer:mime-version:content-type:content-transfer-encoding; b=Q3ITL+zSqZsfxHsm22YnWd/292l1VB/FJVBxXzyuAyRNH0dcGTvZl2hQCCVgLbxEm 7mL0exqmpF35Hv3mT+rEw== X-Nifty-SrcIP: [219.104.15.224] Date: Sun, 14 Oct 2007 10:02:45 +0900 From: Komuro To: davem@sunset.davemloft.net Cc: linux-kernel@vger.kernel.org Subject: Re: [NOT VERY SAFE] [TCP]: Set initial_ssthresh default to zero in Cubic and BIC. Message-Id: <20071014100245.914b784a.komurojun@nifty.com> In-Reply-To: <20071014073658.d4352b8c.komurojun@nifty.com> References: <20071006132601.f944f461.komurojun@nifty.com> <20071014073658.d4352b8c.komurojun@nifty.com> X-Mailer: Sylpheed 2.3.1 (GTK+ 2.10.11; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2461 Lines: 83 Dear David Actually, tcp_sk(sk)->snd_ssthresh is not initialized, if initial_ssthresh is 0. The patch should be static void bictcp_init(struct sock *sk) { bictcp_reset(inet_csk_ca(sk)); - if (initial_ssthresh) - tcp_sk(sk)->snd_ssthresh = initial_ssthresh; + + tcp_sk(sk)->snd_ssthresh = initial_ssthresh; } Best Regards Komuro > > Dear David > > The patch "[TCP]: Set initial_ssthresh default to zero in Cubic and BIC." > is not very safe. > > With this patch, ftp-transfer stops in my system. > (vsftpd-2.0.5-8) > > Please revert this patch. > > > Best Regards > Komuro > > >commit 66e1e3b20cbbf99da63e6c1af0fc6d39c2ed099a > >Author: David S. Miller > >Date: Wed Jun 13 01:03:53 2007 -0700 > > > > [TCP]: Set initial_ssthresh default to zero in Cubic and BIC. > > > > Because of the current default of 100, Cubic and BIC perform very > > poorly compared to standard Reno. > > > > In the worst case, this change makes Cubic and BIC as aggressive as > > Reno. So this change should be very safe. > > > > Signed-off-by: David S. Miller > > > >diff --git a/net/ipv4/tcp_bic.c b/net/ipv4/tcp_bic.c > >index 281c9f9..dd9ef65 100644 > >--- a/net/ipv4/tcp_bic.c > >+++ b/net/ipv4/tcp_bic.c > >@@ -29,7 +29,7 @@ static int fast_convergence = 1; > > static int max_increment = 16; > > static int low_window = 14; > > static int beta = 819; /* = 819/1024 (BICTCP_BETA_SCALE) */ > >-static int initial_ssthresh = 100; > >+static int initial_ssthresh; > > static int smooth_part = 20; > > > > module_param(fast_convergence, int, 0644); > >diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c > >index 1422448..ebfaac2 100644 > >--- a/net/ipv4/tcp_cubic.c > >+++ b/net/ipv4/tcp_cubic.c > >@@ -29,7 +29,7 @@ > > static int fast_convergence __read_mostly = 1; > > static int max_increment __read_mostly = 16; > > static int beta __read_mostly = 819; /* = 819/1024 (BICTCP_BETA_SCALE) */ > >-static int initial_ssthresh __read_mostly = 100; > >+static int initial_ssthresh __read_mostly; > > static int bic_scale __read_mostly = 41; > > static int tcp_friendliness __read_mostly = 1; > > -- Komuro - 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/