From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755977Ab2F2PLM (ORCPT ); Fri, 29 Jun 2012 11:11:12 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:55468 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751446Ab2F2PLL (ORCPT ); Fri, 29 Jun 2012 11:11:11 -0400 Subject: Re: [RFC] [TCP 1/3] tcp: Add MSG_NEW_PACKET flag to indicate preferable packet boundaries From: Eric Dumazet To: Andreas Gruenbacher Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Herbert Xu , "David S. Miller" In-Reply-To: <1340981690.25226.3.camel@gurkel.linbit> References: <1340981690.25226.3.camel@gurkel.linbit> Content-Type: text/plain; charset="UTF-8" Date: Fri, 29 Jun 2012 17:11:06 +0200 Message-ID: <1340982666.21162.3.camel@edumazet-glaptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2012-06-29 at 16:54 +0200, Andreas Gruenbacher wrote: > The MSG_NEW_PACKET flag indicates to sendmsg / sendpage that the message or > page should be put into a new packet even when there is still room left in the > previous packet. > > In the tcp protocol, messages which are not sent immediately are queued. When > more data is sent, it will be added to the last segment in that queue until > that segment is "full" whenever possible; only then is a new segment added. > Right now, there is no way to indicate when tcp should start a new segment. > The new flag allows to control that. > > Signed-off-by: Andreas Gruenbacher > --- I don't understand how maintaining any message boundaries at sender can prevent any middlebox or the receiver to coalesce frames to any boundaries it prefers ?