Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261256AbVAWIRz (ORCPT ); Sun, 23 Jan 2005 03:17:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261257AbVAWIRz (ORCPT ); Sun, 23 Jan 2005 03:17:55 -0500 Received: from opersys.com ([64.40.108.71]:62986 "EHLO www.opersys.com") by vger.kernel.org with ESMTP id S261256AbVAWIRy (ORCPT ); Sun, 23 Jan 2005 03:17:54 -0500 Message-ID: <41F3602E.9050204@opersys.com> Date: Sun, 23 Jan 2005 03:28:30 -0500 From: Karim Yaghmour Reply-To: karim@opersys.com Organization: Opersys inc. User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.2) Gecko/20040805 Netscape/7.2 X-Accept-Language: en-us, en, fr, fr-be, fr-ca, fr-fr MIME-Version: 1.0 To: Roman Zippel CC: Nikita Danilov , linux-kernel@vger.kernel.org, Tom Zanussi Subject: Re: 2.6.11-rc1-mm1 References: <20050114002352.5a038710.akpm@osdl.org> <20050114103836.GA71397@muc.de> <41E7A7A6.3060502@opersys.com> <41E8358A.4030908@opersys.com> <41E899AC.3070705@opersys.com> <41EA0307.6020807@opersys.com> <41EADA11.70403@opersys.com> <41EC2DCA.50904@opersys.com> <41EC8AA2.1030000@opersys.com> <41F0A0A2.1010109@opersys.com> <41F355AD.50901@opersys.com> In-Reply-To: <41F355AD.50901@opersys.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1280 Lines: 32 Karim Yaghmour wrote: > This is not good for any client that doesn't know beforehand the exact > size of their data units, as in the case of LTT. If LTT has to use this > code that means we are going to loose performance because we will need to > fill an intermediate data structure which will only be used for relay_write(). > Instead of zero-copy, we would have an extra unnecessary copy. There has > got to be a way for clients to directly reserve and write as they wish. > Even Zach Brown recognized this in his tracepipe proposal, here's from > his patch: > + * - let caller reserve space and get a pointer into buf Also, if the reserve is exported, then a client that chooses so, can do something like: local_irq_save(); relay_reserve(); write(); write(); write(); ... local_irq_restore(); And therefore enforce in-order events is he so chooses. Karim -- Author, Speaker, Developer, Consultant Pushing Embedded and Real-Time Linux Systems Beyond the Limits http://www.opersys.com || karim@opersys.com || 1-866-677-4546 - 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/