From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f54.google.com ([209.85.160.54]:39283 "EHLO mail-pl0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751282AbeCLTsQ (ORCPT ); Mon, 12 Mar 2018 15:48:16 -0400 Received: by mail-pl0-f54.google.com with SMTP id s13-v6so9936730plq.6 for ; Mon, 12 Mar 2018 12:48:16 -0700 (PDT) Date: Mon, 12 Mar 2018 12:48:13 -0700 From: Stephen Hemminger To: David Miller Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org Subject: Re: de-indirect TCP congestion control Message-ID: <20180312124813.3fa6b833@xeon-e3> In-Reply-To: <20180312.150406.1432667769589045118.davem@davemloft.net> References: <20180312114552.3f51e6ac@xeon-e3> <20180312.150406.1432667769589045118.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org List-ID: 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.