From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next] tcp: shrink tcp6_timewait_sock by one cache line Date: Thu, 03 Oct 2013 16:02:52 -0400 (EDT) Message-ID: <20131003.160252.2071364130742864278.davem@davemloft.net> References: <1380711604.19002.78.camel@edumazet-glaptop.roam.corp.google.com> <20131003.153158.1558578931500427624.davem@davemloft.net> <1380829642.19002.225.camel@edumazet-glaptop.roam.corp.google.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: eric.dumazet@gmail.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:38701 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754976Ab3JCUCy (ORCPT ); Thu, 3 Oct 2013 16:02:54 -0400 In-Reply-To: <1380829642.19002.225.camel@edumazet-glaptop.roam.corp.google.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet Date: Thu, 03 Oct 2013 12:47:22 -0700 > On Thu, 2013-10-03 at 15:31 -0400, David Miller wrote: > >> Eric just use tcp_time_stamp in all of these locations, then you can >> lose the casts and still achieve your stated objective. > > I thought about this, but this would break if tcp_time_stamp was no > longer tied to jiffies. > > Van Jacobson had the idea of using finer resolution tcp_time_stamp for > TCP flows in data centers, for better RTT estimation and and cwin > control, but also for better diagnostics. > > Note we used this (u32)jiffies thing in net/ipv4/inetpeer.c in the past, > and tp->tso_deferred is also a u32 value. I am sure that you could define a set of interfaces which are named such that the intent and usage is clear, would do the u32 cast, and would be updated by whoever changes the timestamp implementation in the future. The cast is really ugly, even if we do it in inetpeer already, and you're already here cleaning things up, so please do it right. Thank you.