From mboxrd@z Thu Jan 1 00:00:00 1970 From: Komuro Subject: Re: [NOT VERY SAFE] [TCP]: Set initial_ssthresh default to zero in Cubic and BIC. Date: Sun, 14 Oct 2007 13:28:51 +0900 Message-ID: <20071014132851.8d6a9de3.komurojun@nifty.com> References: <20071006132601.f944f461.komurojun@nifty.com> <20071014073658.d4352b8c.komurojun@nifty.com> <20071014100245.914b784a.komurojun@nifty.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: davem@sunset.davemloft.net Return-path: In-Reply-To: <20071014100245.914b784a.komurojun@nifty.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Dear David >Komuro, every single email I sent to you bounces with "user unknown", >I bet it is some spam filter or similar that doesn't like the >fact that I lack reverse DNS. >>From mailing-list-archive, I can read your email. Best Regards Komuro > 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 -- Komuro