From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: CLOCK_MONOTONIC datagram timestamps by the kernel Date: Thu, 01 Mar 2007 07:54:44 -0800 Message-ID: <45E6F744.8070106@linux-foundation.org> References: <45E5570E.7050301@free.fr> <200702281555.10309.dada1@cosmosbay.com> <45E5A8AE.3030606@free.fr> <200703011230.50596.dada1@cosmosbay.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: John find , linux-net@vger.kernel.org, netdev@vger.kernel.org To: Eric Dumazet Return-path: Received: from smtp.osdl.org ([65.172.181.24]:57804 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933263AbXCAPzr (ORCPT ); Thu, 1 Mar 2007 10:55:47 -0500 In-Reply-To: <200703011230.50596.dada1@cosmosbay.com> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Eric Dumazet wrote: > On Wednesday 28 February 2007 17:07, John wrote: > > >> Consider an idle Linux 2.6.20-rt8 system, equipped with a single PCI-E >> gigabit Ethernet NIC, running on a modern CPU (e.g. Core 2 Duo E6700). >> All this system does is time stamp 1000 packets per second. >> >> Are you claiming that this platform *cannot* handle most packets within >> less than 1 microsecond of their arrival? >> > > Yes I claim it. > > You expect too much of this platform, unless "most" means 10 % for > you ;) > > If you replace "1 us" by "50 us", then yes, it probably can do it, if "most" > means 99%, (not 99.999 %) > > Anyway, if you want to play, you can apply this patch on top of > linux-2.6.21-rc2 (nanosecond resolution infrastruture needs 2.6.21) > I let you do the adjustments for rt kernel. > > I like it except changing stamp to stampns all over the place is unnecessary, just change the type. > I compiled it on my i386 machine, and tested it with a patched libpcap/tcpdump > > I assume old tcpdump works as expected.