Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966065AbcDLURj (ORCPT ); Tue, 12 Apr 2016 16:17:39 -0400 Received: from mail-pf0-f181.google.com ([209.85.192.181]:36354 "EHLO mail-pf0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964972AbcDLURf (ORCPT ); Tue, 12 Apr 2016 16:17:35 -0400 Message-ID: <1460492253.6473.596.camel@edumazet-glaptop3.roam.corp.google.com> Subject: Re: TCP reaching to maximum throughput after a long time From: Eric Dumazet To: Ben Greear Cc: "Machani, Yaniv" , netdev , "David S. Miller" , Eric Dumazet , Neal Cardwell , Yuchung Cheng , Nandita Dukkipati , open list , "Kama, Meirav" Date: Tue, 12 Apr 2016 13:17:33 -0700 In-Reply-To: <570D566B.8050302@candelatech.com> References: <1460472764.6473.589.camel@edumazet-glaptop3.roam.corp.google.com> <570D0E94.3080006@candelatech.com> <570D566B.8050302@candelatech.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1352 Lines: 36 On Tue, 2016-04-12 at 13:11 -0700, Ben Greear wrote: > On 04/12/2016 12:31 PM, Machani, Yaniv wrote: > > On Tue, Apr 12, 2016 at 18:04:52, Ben Greear wrote: > >> On 04/12/2016 07:52 AM, Eric Dumazet wrote: > >>> On Tue, 2016-04-12 at 12:17 +0000, Machani, Yaniv wrote: > >>>> > >> > >> If you are using 'Cubic' TCP congestion control, then please try > >> something different. > >> It was broken last I checked, at least when used with the ath10k driver. > >> > > > > Thanks Ben, this indeed seems to be the issue ! > > Switching to reno got me to max throughput instantly. > > > > I'm still looking through the thread you have shared, but from what I understand there is no planned fix for it ? > > I think at the time it was blamed on ath10k and no one cared to try to fix it. > > Or, maybe no one really uses CUBIC anymore? > > Either way, I have no plans to try to fix CUBIC, but maybe someone who knows > this code better could give it a try. Well, cubic seems to work in many cases, assuming they are not too many drops. Assuming one flow can get nominal speed in few RTT is kind a dream, and so far nobody claimed a CC was able to do that, while still being fair and resilient. TCP CC are full of heuristics, and by definition heuristics that were working 6 years ago might need to be refreshed. We are still maintaining Cubic for sure.