From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755218AbYHMUXd (ORCPT ); Wed, 13 Aug 2008 16:23:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752891AbYHMUXT (ORCPT ); Wed, 13 Aug 2008 16:23:19 -0400 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:46026 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752675AbYHMUXS (ORCPT ); Wed, 13 Aug 2008 16:23:18 -0400 Date: Wed, 13 Aug 2008 13:23:19 -0700 (PDT) Message-Id: <20080813.132319.175666454.davem@davemloft.net> To: vst@vlnb.net Cc: open-iscsi@googlegroups.com, rdreier@cisco.com, rick.jones2@hp.com, jgarzik@pobox.com, swise@opengridcomputing.com, kxie@chelsio.com, netdev@vger.kernel.org, michaelc@cs.wisc.edu, daisyc@us.ibm.com, wenxiong@us.ibm.com, bhua@us.ibm.com, dm@chelsio.com, leedom@chelsio.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC][PATCH 1/1] cxgb3i: cxgb3 iSCSI initiator From: David Miller In-Reply-To: <48A32976.7060504@vlnb.net> References: <20080812.150246.42068558.davem@davemloft.net> <200808121521.10101.divy@chelsio.com> <48A32976.7060504@vlnb.net> X-Mailer: Mew version 5.2 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: Vladislav Bolkhovitin Date: Wed, 13 Aug 2008 22:35:34 +0400 > This is because the target sends data in a zero-copy manner, so its > CPU is capable to deal with the load, but on the initiator there are > additional data copies from skb's to page cache and from page cache > to application. If you've actually been reading at all what I've been saying in this thread you'll see that I've described a method to do this copy avoidance in a completely stateless manner. You don't need to implement a TCP stack in the card in order to do data placement optimizations. They can be done completely stateless. Also, large portions of the cpu overhead are transactional costs, which are significantly reduced by existing technologies such as LRO.