Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752963AbdHISbT (ORCPT ); Wed, 9 Aug 2017 14:31:19 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:57210 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752564AbdHISPR (ORCPT ); Wed, 9 Aug 2017 14:15:17 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Neal Cardwell , Yuchung Cheng , Soheil Hassas Yeganeh , "David S. Miller" Subject: [PATCH 4.9 36/93] tcp_bbr: cut pacing rate only if filled pipe Date: Wed, 9 Aug 2017 11:13:29 -0700 Message-Id: <20170809181337.124566769@linuxfoundation.org> X-Mailer: git-send-email 2.14.0 In-Reply-To: <20170809181335.658857427@linuxfoundation.org> References: <20170809181335.658857427@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1820 Lines: 48 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Neal Cardwell [ Upstream commit 4aea287e90dd61a48268ff2994b56f9799441b62 ] In bbr_set_pacing_rate(), which decides whether to cut the pacing rate, there was some code that considered exiting STARTUP to be equivalent to the notion of filling the pipe (i.e., bbr_full_bw_reached()). Specifically, as the code was structured, exiting STARTUP and going into PROBE_RTT could cause us to cut the pacing rate down to something silly and low, based on whatever bandwidth samples we've had so far, when it's possible that all of them have been small app-limited bandwidth samples that are not representative of the bandwidth available in the path. (The code was correct at the time it was written, but the state machine changed without this spot being adjusted correspondingly.) Fixes: 0f8782ea1497 ("tcp_bbr: add BBR congestion control") Signed-off-by: Neal Cardwell Signed-off-by: Yuchung Cheng Signed-off-by: Soheil Hassas Yeganeh Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp_bbr.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/net/ipv4/tcp_bbr.c +++ b/net/ipv4/tcp_bbr.c @@ -191,12 +191,11 @@ static u64 bbr_rate_bytes_per_sec(struct */ static void bbr_set_pacing_rate(struct sock *sk, u32 bw, int gain) { - struct bbr *bbr = inet_csk_ca(sk); u64 rate = bw; rate = bbr_rate_bytes_per_sec(sk, rate, gain); rate = min_t(u64, rate, sk->sk_max_pacing_rate); - if (bbr->mode != BBR_STARTUP || rate > sk->sk_pacing_rate) + if (bbr_full_bw_reached(sk) || rate > sk->sk_pacing_rate) sk->sk_pacing_rate = rate; }