Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754077Ab0BRJen (ORCPT ); Thu, 18 Feb 2010 04:34:43 -0500 Received: from host64.kissl.de ([213.239.241.64]:40292 "EHLO host64.kissl.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753422Ab0BRJem (ORCPT ); Thu, 18 Feb 2010 04:34:42 -0500 Message-ID: <4B7D01CE.1030101@lastsummer.de> Date: Thu, 18 Feb 2010 10:01:02 +0100 From: Franco Fichtner User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: Andreas Petlund CC: =?ISO-8859-1?Q?Ilpo_J=E4rvinen?= , Netdev , eric.dumazet@gmail.com, hannemann@nets.rwth-aachen.de, LKML , shemminger@vyatta.com, william.allen.simpson@gmail.com, damian@tvk.rwth-aachen.de, ebiederm@xmission.com, David Miller Subject: Re: [net-next PATCH v4 2/3] net: TCP thin linear timeouts References: <4B7AAE69.8020701@simula.no> <20100217.163255.133898079.davem@davemloft.net> <4B7CFDE4.4010003@simula.no> In-Reply-To: <4B7CFDE4.4010003@simula.no> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1896 Lines: 62 Hi, Andreas Petlund wrote: > On 02/18/2010 09:41 AM, Ilpo J?rvinen wrote: > >> On Wed, 17 Feb 2010, David Miller wrote: >> >> >>> From: Andreas Petlund >>> Date: Tue, 16 Feb 2010 15:40:41 +0100 >>> >>> >>>> @@ -341,6 +342,8 @@ struct tcp_sock { >>>> u16 advmss; /* Advertised MSS */ >>>> u8 frto_counter; /* Number of new acks after RTO */ >>>> u8 nonagle; /* Disable Nagle algorithm? */ >>>> + u8 thin_lto : 1,/* Use linear timeouts for thin streams */ >>>> + thin_undef : 7; >>>> >>>> >>> There is now a gap of 3 unused bytes here in this critical >>> core TCP socket data structure. >>> >>> Please either find a way to avoid this hole, or document >>> it with a comment. >>> >> There would be multiple bits free for use in both frto_counter and nonagle >> byte. >> >> > > I was playing aroud with this setup: > > ========= > u8 nonagle : 4,/* Disable Nagle algorithm? */ > thin_lto : 1,/* Use linear timeouts for thin streams */ > thin_dupack : 1,/* Fast retransmit on first dupack */ > thin_undef : 2; > ========= > > Do you think that would do the trick? > According to Ilpo, it would be ok to reduce both ftro_counter and nonagle, so why not join all these into u16 and leave the remaining free bits documented for other people. Like this: u16 frto_counter:x; /* Number of new acks after RTO */ u16 nonagle:y; /* Disable Nagle algorithm? */ u16 thin_lto:1; /* Use linear timeouts for thin streams */ u16 unused:15-x-y; Not sure about the y and x. Ilpo, can you comment on those values? Thanks, Franco -- 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/