From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [net-next 0/6] tcp: remove prequeue and header prediction Date: Mon, 31 Jul 2017 14:38:07 -0700 (PDT) Message-ID: <20170731.143807.1921676369334873438.davem@davemloft.net> References: <20170730015723.25587-1-fw@strlen.de> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: fw@strlen.de Return-path: Received: from shards.monkeyblade.net ([184.105.139.130]:45914 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751632AbdGaViI (ORCPT ); Mon, 31 Jul 2017 17:38:08 -0400 In-Reply-To: <20170730015723.25587-1-fw@strlen.de> Sender: netdev-owner@vger.kernel.org List-ID: From: Florian Westphal Date: Sun, 30 Jul 2017 03:57:17 +0200 > During a hallway discussion with Eric Dumazet at Netdev 1.2 in > Tokyo some maybe-not-so-useful-anymore TCP stack features came up, > among these header prediction and prequeueing. > > In brief, TCP prequeue assumes a single-process-blocking-read design, > which is not that common anymore. The most frequently used high-performance > networking program that is an excellent fit for these features is netperf. > > The idea behind prequeueing is to move part of tcp processing, including > retransmit queue cleaning, to process context. > > With (e)poll designs, prequeue is always skipped, so for such programs > this is dead-code removal. > > Header prediction is also less useful nowadays. > For packet trains, GRO will do packet aggregation so we do not get the > per-packet benefit that this had before GRO anymore. > > Because of SACK, header prediction also will be ineffective once > a connection suffers even light packet losses. > > code removal aside, after this change processing always occurs in BH > context, this allows to experiment e.g. with doing bulk freeing of > skb heads when incoming ACKs clean packets from the retransmit queue. > > There are no changes since the RFC, except in last patch (i missed > another no-longer-used mib counter). I also edited a few commit messages. Series applied, thanks a lot for doing this.