From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Sidorenko Subject: Re: An inconsistency/bug in ingress netem timestamps Date: Wed, 15 Apr 2009 16:10:43 -0400 Message-ID: <200904151610.43980.alexandre.sidorenko@hp.com> References: <20090415195022.GA3322@ami.dom.local> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: "netdev@vger.kernel.org" To: Jarek Poplawski Return-path: Received: from g1t0027.austin.hp.com ([15.216.28.34]:43973 "EHLO g1t0027.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753457AbZDOUKq (ORCPT ); Wed, 15 Apr 2009 16:10:46 -0400 In-Reply-To: <20090415195022.GA3322@ami.dom.local> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: On April 15, 2009 03:50:22 pm Jarek Poplawski wrote: > I agree there is an inconsistency, but it seems 100 ms isn't the > "right" thing to show here. It shows an internal delay added on ifb by > any packet scheduler, so probably not what a user usually expects. Hi Jarek, thank you for your comments. Yes, I understand that it just looked OK in this case even though technically the value was not quite correct. > > The strange thing is that as soon as there is any ptype_all handler > > installed, skb->tstamp is updated properly. Unfortunately, my knowledge > > of TC internals is not good enough to find how exactly this happens. > > Isn't it when act_mirred calls dev_queue_xmit with dev_queue_xmit_nit? > But, as above mentioned, I doubt it's "updated properly" in this case. I can see that dev_queue_xmit_nit calls net_timestamp(skb) unconditionally. I agree that to fix this properly we need to update tstamp in another place explicitly (in ifb or netem?). Thanks, Alex -- ------------------------------------------------------------------ Alexandre Sidorenko email: asid@hp.com WTEC Linux Hewlett-Packard (Canada) ------------------------------------------------------------------