From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH 0/9]: tcp-2.6 patchset Date: Tue, 29 May 2007 13:19:51 -0700 Message-ID: <20070529131951.1d9a5b84@freepuppy> References: <11801685622325-git-send-email-ilpo.jarvinen@helsinki.fi> <20070526.164418.115928217.davem@davemloft.net> <20070527.021104.74747736.davem@davemloft.net> <20070527140430.GA30299@galon.ev-en.org> <20070529091415.03a14216@freepuppy> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Baruch Even , David Miller , Herbert Xu , Netdev To: "Ilpo =?UTF-8?B?SsOkcnZpbmVuIg==?= "@smtp.osdl.org Return-path: Received: from smtp.osdl.org ([207.189.120.12]:41384 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758244AbXE2U2g convert rfc822-to-8bit (ORCPT ); Tue, 29 May 2007 16:28:36 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, 29 May 2007 23:07:00 +0300 (EEST) "Ilpo J=C3=A4rvinen" wrote: > On Tue, 29 May 2007, Stephen Hemminger wrote: >=20 > > On Mon, 28 May 2007 13:27:03 +0300 (EEST) > > "Ilpo J=C3=A4rvinen" wrote: > >=20 > > > On Sun, 27 May 2007, Ilpo J=C3=A4rvinen wrote: > > >=20 > > > [PATCH] [TCP]: Fix GSO ignorance of pkts_acked arg (cong.cntrl mo= dules) > >=20 > > Yes, thanks for fixing this. Wonder how it affects measurements. >=20 > ...It's a bit hard to tell since dynamics change so dramatically=20 > in > 0 check cases, the resulting behavior in too small value cases > may be easier to predict... It's possible that this could explain som= e=20 > anomalities you've been seeing in your measurements. >=20 > > > It is not very clear how SYN segments should be handled, so I > > > choose to follow the previous implementation in this respect. > >=20 > > Since we don't invoke congestion control modules until after the SY= N > > handshake this is not a problem. >=20 > Just curious, do you mean that cc modules cannot measure, e.g., initi= al > RTT through this mechanism (though they could do that in init() cb th= en > I suppose)... Or do you mean that they are called already for the ACK > that completes the SYN handshake and therefore its skb is being clean= ed=20 > from the queue right now (this is the case I above refer to)?=20 > In the first case the decrementer code is NOP. If the latter, then it > is just interface specification question, i.e., if SYNs are treated a= s=20 > zero or one in num_acked for the pkts_acked callback (I have no opini= on > on this but was just trying to make sure cc modules get what they > expect :-)).=20 We don't switch a socket out of Reno until after the initial handshake. It evolved that way, and has a couple of advantages: * uncomplete connections don't up module refcount so it is easier to debug * in future, we can choose congestion control to use based on route metric. =20 As an interface, it makes sense to keep the API with the SYN counting as a packet. --=20 Stephen Hemminger