From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: why does skb->tstamp use getnstimeofday? Date: Mon, 16 Jan 2012 14:05:21 -0800 Message-ID: <4F149F21.70400@hp.com> References: <1326645750.5287.48.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , netdev@vger.kernel.org To: Anatoly Sivov Return-path: Received: from g4t0014.houston.hp.com ([15.201.24.17]:7919 "EHLO g4t0014.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932069Ab2APWFX (ORCPT ); Mon, 16 Jan 2012 17:05:23 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 01/15/2012 09:55 AM, Anatoly Sivov wrote: > I missed that field tstamp is used for things other than RTT and can be > even user-spaced with SO_TIMESTAMP. > However, timekeeper speed up/slow down (due to ntp) can seriously affect > some congestion avoidance algorithm quality, I guess. > Am I wrong? Good question - not sure if we will see anything, but the upcoming leap-second might be interesting to watch - though I think contemporary NTP addresses that by a big slew rather than a step adjust. Of course it can step-adjust the time on the system, but 99 times out of 10 (*) that will be just at system start-up, when there probably will not be all that many congestion controlled connections active. Of course, who knows what that 100th out of 10 times will do. rick jones * 99 times out of 10 is an expression which if I recall correctly was coined or at least repeated by a high-school sports coach to mean "virtually all of the time"