From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 28 Apr 2001 19:53:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 28 Apr 2001 19:53:00 -0400 Received: from www.linux.org.uk ([195.92.249.252]:24082 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id ; Sat, 28 Apr 2001 19:52:44 -0400 Date: Sun, 29 Apr 2001 00:52:06 +0100 From: Russell King To: linux-kernel@vger.kernel.org Subject: Zerocopy implementation issues Message-ID: <20010429005206.J21792@flint.arm.linux.org.uk> Mail-Followup-To: Russell King , linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, Can someone please explain to me the rationale behind the zerocopy implementation that has appeared in 2.4.4 please? The reason I ask is that even on x86, it seems to me to be extremely silly to have the expense of doing unaligned checksumming for the gain of zerocopy. Just think - if you did checksumming on aligned word boundaries you could be far faster! (Yes, you guessed it, its broken on ARM, and is going to make the networking layer pig slow if we keep the current implementation as it stands due to the phenominal amount of exceptions it _will_ generate - 1 exception per word in a packet). I'm still investigating the source of the networking corruptions I'm seeing, but its looking like the above is the reason (data is being corrupted on TCP send). -- Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux http://www.arm.linux.org.uk/personal/aboutme.html