From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f171.google.com ([209.85.192.171]:35350 "EHLO mail-pf0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751282AbeCLUDi (ORCPT ); Mon, 12 Mar 2018 16:03:38 -0400 Received: by mail-pf0-f171.google.com with SMTP id y186so4843083pfb.2 for ; Mon, 12 Mar 2018 13:03:37 -0700 (PDT) Subject: Re: de-indirect TCP congestion control To: Stephen Hemminger , David Miller Cc: netdev@vger.kernel.org References: <20180312114552.3f51e6ac@xeon-e3> <20180312.150406.1432667769589045118.davem@davemloft.net> <20180312124813.3fa6b833@xeon-e3> From: Eric Dumazet Message-ID: Date: Mon, 12 Mar 2018 13:03:35 -0700 MIME-Version: 1.0 In-Reply-To: <20180312124813.3fa6b833@xeon-e3> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org List-ID: On 03/12/2018 12:48 PM, Stephen Hemminger wrote: > On Mon, 12 Mar 2018 15:04:06 -0400 (EDT) > David Miller wrote: > >> From: Stephen Hemminger >> Date: Mon, 12 Mar 2018 11:45:52 -0700 >> >>> Since indirect calls are expensive, and now even more so, perhaps we should figure out >>> a way to make the default TCP congestion control hooks into direct calls. >>> 99% of the users just use the single CC module compiled into the kernel. >> >> Who is this magic user with only one CC algorithm enabled in their >> kernel? I want to know who this dude is? >> >> I don't think it's going to help much since people will have I think >> at least two algorithms compiled into nearly everyone's tree. >> >> Distributions will enable everything. >> >> Google is going to have at least two algorithms enabled. >> >> etc. etc. etc. >> >> Getting rid of indirect calls is a fine goal, but the precondition you >> are mentioning to achieve this doesn't seem practical at all. > > What I meant is that kernels with N congestion controls, almost all traffic > uses the default So that path can be optimized. The example I gave would > have all the others doing the same indirect call. > I do not understand. What is default_tcp_ops anyway ? How changes to /proc/sys/net/ipv4/tcp_congestion_control will impact this ?