From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262002AbULVQFt (ORCPT ); Wed, 22 Dec 2004 11:05:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262004AbULVQFl (ORCPT ); Wed, 22 Dec 2004 11:05:41 -0500 Received: from ra.tuxdriver.com ([24.172.12.4]:60681 "EHLO ra.tuxdriver.com") by vger.kernel.org with ESMTP id S262002AbULVQFY (ORCPT ); Wed, 22 Dec 2004 11:05:24 -0500 Date: Wed, 22 Dec 2004 11:06:27 -0500 From: "John W. Linville" To: Martijn van Oosterhout Cc: Mandeep Sandhu , dima@s2io.com, Jeff Garzik , linux-newbie@vger.kernel.org, linux-net@vger.kernel.org, linux-kernel@vger.kernel.org, kernelnewbies Subject: Re: zero copy issue while receiving the data (counter part of sendfil e) Message-ID: <20041222160625.GB19449@tuxdriver.com> Mail-Followup-To: Martijn van Oosterhout , Mandeep Sandhu , dima@s2io.com, Jeff Garzik , linux-newbie@vger.kernel.org, linux-net@vger.kernel.org, linux-kernel@vger.kernel.org, kernelnewbies References: <267988DEACEC5A4D86D5FCD780313FBB02C66FCA@exch-03.noida.hcltech.com> <1103649767.7217.100.camel@beastie> <41C879CB.3040600@pobox.com> <1103658190.7217.121.camel@beastie> <1103703718.3775.93.camel@samish.india.ascend.com> <20041222155003.GA29278@svana.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20041222155003.GA29278@svana.org> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 22, 2004 at 04:50:05PM +0100, Martijn van Oosterhout wrote: > Generally, reading from memory takes time because the CPU has to wait, > writing is free since it can be deferred in the cache (in theory > indefinitly) until there's free cycle. I'm not sure I'd call that "free" -- executing the instructions for the write has a non-zero cost. Still, it is significantly cheaper than the read... John -- John W. Linville linville@tuxdriver.com