From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH 2.6.25 1/1]S2io: Multiqueue network device support implementation Date: Wed, 23 Jan 2008 23:30:06 -0800 (PST) Message-ID: <20080123.233006.124819204.davem@davemloft.net> References: <78C9135A3D2ECE4B8162EBDCE82CAD7702E70E92@nekter> <20080124072549.GA6814@one.firstfloor.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: Ramkrishna.Vepa@neterion.com, Sreenivasa.Honnur@neterion.com, netdev@vger.kernel.org, jeff@garzik.org, support@neterion.com To: andi@firstfloor.org Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:60184 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752597AbYAXH35 (ORCPT ); Thu, 24 Jan 2008 02:29:57 -0500 In-Reply-To: <20080124072549.GA6814@one.firstfloor.org> Sender: netdev-owner@vger.kernel.org List-ID: From: Andi Kleen Date: Thu, 24 Jan 2008 08:25:49 +0100 > > have done away with handling tx completion in the interrupt handler, and > > are instead handling them in the context of the transmit. The slow path, > > straggling transmit completions will be handled in the timer context. > > Ok -- hopefully you don't have bad corner cases from this when the pipe > is not fully filled and then causing longer latencies on completion. > Old NAPI sometimes suffered from such problems. BTW, such a TX completion timer will stall TCP sockets when the TX queue of the device is partially filled and then sending stops. TX ring SKB liberation really must be done in a very small finite amount of time in order to avoid this problem properly. Deferring it to HZ granular timers doesn't give a quick enough response, especially at high packet rates.