Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754285AbcDMDIt (ORCPT ); Tue, 12 Apr 2016 23:08:49 -0400 Received: from mail-wm0-f42.google.com ([74.125.82.42]:36768 "EHLO mail-wm0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751648AbcDMDIr (ORCPT ); Tue, 12 Apr 2016 23:08:47 -0400 MIME-Version: 1.0 In-Reply-To: <570D6B39.3050605@candelatech.com> References: <1460472764.6473.589.camel@edumazet-glaptop3.roam.corp.google.com> <570D0E94.3080006@candelatech.com> <570D566B.8050302@candelatech.com> <1460492253.6473.596.camel@edumazet-glaptop3.roam.corp.google.com> <570D5944.5070100@candelatech.com> <1460492999.6473.599.camel@edumazet-glaptop3.roam.corp.google.com> <570D6B39.3050605@candelatech.com> From: Yuchung Cheng Date: Tue, 12 Apr 2016 20:08:06 -0700 Message-ID: Subject: Re: TCP reaching to maximum throughput after a long time To: Ben Greear Cc: Eric Dumazet , "Machani, Yaniv" , netdev , "David S. Miller" , Eric Dumazet , Neal Cardwell , Nandita Dukkipati , open list , "Kama, Meirav" 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: 1733 Lines: 54 On Tue, Apr 12, 2016 at 2:40 PM, Ben Greear wrote: > On 04/12/2016 01:29 PM, Eric Dumazet wrote: >> >> On Tue, 2016-04-12 at 13:23 -0700, Ben Greear wrote: >> >>> It worked well enough for years that I didn't even know other algorithms >>> were >>> available. It was broken around 4.0 time, and I reported it to the list, >>> and no one seemed to really care enough to do anything about it. I >>> changed >>> to reno and ignored the problem as well. >>> >>> It is trivially easy to see the regression when using ath10k NIC, and >>> from this email >>> thread, I guess other NICs have similar issues. >> >> >> Since it is so trivial, why don't you start a bisection ? > > > I vaguely remember doing a bisect, but I can't find any email about > that, so maybe I didn't. At any rate, it is somewhere between 3.17 and 4.0. > From memory, it was between 3.19 and 4.0, but I am not certain of that. > > Neil's suggestion, from the thread below, is that it was likely: "605ad7f > tcp: refine TSO autosizing" > > Here is previous email thread: > > https://www.mail-archive.com/netdev@vger.kernel.org/msg80803.html > > This one has a link to a pcap I made at the time: > > https://www.mail-archive.com/netdev@vger.kernel.org/msg80890.html based on the prev thread I propose we disable hystart ack-train. It is brittle under various circumstances. We've disabled that at Google for years. > >> >> I asked a capture, I did not say ' switch to Reno or whatever ', right ? >> >> Guessing is nice, but investigating and fixing is better. >> >> Do not assume that nothing can be done, please ? > > > Thanks, > Ben > > -- > Ben Greear > Candela Technologies Inc http://www.candelatech.com >