From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755725AbZA0Smd (ORCPT ); Tue, 27 Jan 2009 13:42:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755974AbZA0SmO (ORCPT ); Tue, 27 Jan 2009 13:42:14 -0500 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:54832 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1755920AbZA0SmM (ORCPT ); Tue, 27 Jan 2009 13:42:12 -0500 Date: Tue, 27 Jan 2009 10:42:10 -0800 (PST) Message-Id: <20090127.104210.136585415.davem@davemloft.net> To: zbr@ioremap.net Cc: jarkao2@gmail.com, herbert@gondor.apana.org.au, w@1wt.eu, dada1@cosmosbay.com, ben@zeus.com, mingo@elte.hu, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, jens.axboe@oracle.com Subject: Re: [PATCH v2] tcp: splice as many packets as possible at once From: David Miller In-Reply-To: <20090126.221056.174077798.davem@davemloft.net> References: <20090126082036.GB4183@ff.dom.local> <20090126212130.GA4338@ioremap.net> <20090126.221056.174077798.davem@davemloft.net> X-Mailer: Mew version 6.1 on Emacs 22.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: David Miller Date: Mon, 26 Jan 2009 22:10:56 -0800 (PST) > Even for drivers like NIU and myri10ge that do this, they only > use heuristics or some fixed minimum to decide how much to > move to the linear area. > > Result? Some data payload bits end up there because it overshoots. ... > I did test this with the NIU driver at one point, and it did not > change TCP latency nor throughput at all even at 10g speeds. As a followup, it turns out that NIU right now does this properly. It only pulls a maximum of ETH_HLEN into the linear area before giving the SKB to netif_receive_skb().