From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: [PATCH net-next 0/6] kcm: Kernel Connection Multiplexor (KCM) Date: Tue, 24 Nov 2015 12:25:39 +0100 Message-ID: <87y4dnfxl8.fsf@stressinduktion.org> References: <1448054520-1464587-1-git-send-email-tom@herbertland.com> <1448272388.3983270.447381049.07BA3A5C@webmail.messagingengine.com> <20151123.145433.1554000376541433305.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain Cc: netdev@vger.kernel.org, kernel-team@fb.com, davewatson@fb.com, alexei.starovoitov@gmail.com To: David Miller , tom@herbertland.com Return-path: Received: from out2-smtp.messagingengine.com ([66.111.4.26]:49238 "EHLO out2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751797AbbKXLZl (ORCPT ); Tue, 24 Nov 2015 06:25:41 -0500 Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailout.nyi.internal (Postfix) with ESMTP id 190FF20DC6 for ; Tue, 24 Nov 2015 06:25:41 -0500 (EST) In-Reply-To: <20151123.145433.1554000376541433305.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: Hello, David Miller writes: > From: Tom Herbert > Date: Mon, 23 Nov 2015 09:33:44 -0800 > >> The TCP PSH flag is not defined for message delineation (neither is >> urgent pointer). We can't change that (many people have tried to add >> message semantics to TCP protocol but have always failed miserably). > > Agreed. > > My only gripe with kcm right now is a lack of a native sendpage. > We should be able to zero copy data through KCM streams without > any problems whatsoever. I understood from Tom's last mail that the messages are being constructed *in kernel memory* before sending out of the tcp socket. What advantage gives sendpage? The message construction must actually happen before to fill in the necessary headers for the length, so receiver can dissect again. Streaming semantics don't really fit here? Bye, Hannes