Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754690Ab1BXHux (ORCPT ); Thu, 24 Feb 2011 02:50:53 -0500 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:57197 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754387Ab1BXHuw (ORCPT ); Thu, 24 Feb 2011 02:50:52 -0500 Date: Wed, 23 Feb 2011 23:51:29 -0800 (PST) Message-Id: <20110223.235129.02262510.davem@davemloft.net> To: ratbert.chuang@gmail.com Cc: mirqus@gmail.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bhutchings@solarflare.com, eric.dumazet@gmail.com, joe@perches.com, dilinger@queued.net, ratbert@faraday-tech.com Subject: Re: [PATCH v4] net: add Faraday FTMAC100 10/100 Ethernet driver From: David Miller In-Reply-To: References: <20110131.203556.193730771.davem@davemloft.net> X-Mailer: Mew version 6.3 on Emacs 23.1 / Mule 6.0 (HANACHIRUSATO) 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 Content-Length: 910 Lines: 22 From: Po-Yu Chuang Date: Thu, 24 Feb 2011 15:27:55 +0800 > I guess the problem is because a HW restriction that the rx buffer must be > 64 bits aligned. Since I cannot make rx buffer starts at offset 2 bytes, the > IP header, TCP header and data are not 4 bytes aligned. The performance > drops drastically. I cannot believe that after 20 years of commodity ethernet networking chips were first designed, people are still designing hardware that doesn't do this right. Just emit garbage bytes into the sub-word alignment padding if the chip wants to word align it's DMA writes. Even the 15 year old Dec Tulip chips do this properly. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/