From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Naab Subject: Re: [PATCH 2/2] net: netem: always adjust now/delay when not reordering Date: Wed, 21 Aug 2013 17:17:06 +0200 Message-ID: <5214D9F2.90900@stusta.de> References: <1377011469-26151-1-git-send-email-mailings@hupie.com> <1377011469-26151-2-git-send-email-mailings@hupie.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com To: mailings@hupie.com Return-path: Received: from mail.stusta.mhn.de ([141.84.69.5]:32952 "EHLO mail.stusta.mhn.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751618Ab3HUPXx (ORCPT ); Wed, 21 Aug 2013 11:23:53 -0400 In-Reply-To: <1377011469-26151-2-git-send-email-mailings@hupie.com> Sender: netdev-owner@vger.kernel.org List-ID: On 08/20/2013 05:11 PM, Ferry Huberts wrote: > From: Ferry Huberts > > Not doing this (current behaviour) introduces reordering. > > The packet_len_2_sched_time call is the only thing that logically > depends on q->rate, so move the now/delay adjustment out of the if. > > Signed-off-by: Ferry Huberts > --- Hi, The documentation for netem does explicitly mention the reordering with jitter, and gives instructions on how to avoid it. (I have not tested if it works as intended). http://www.linuxfoundation.org/collaborate/workgroups/networking/netem#How_to_reorder_packets_based_on_jitter.3F Could you test if that fixes your problem already? Assuming that the documentation is right: For the sake of stability I strongly oppose changing existing and documented behavior without opt-in. (Then again I'm not involved in kernel development.) If the documentation turns out to be wrong: The netem rate extension (with all the reordering changes for that case, which are needed for proper rate emulation in that model) was introduced in 3.3 by Hagen Paul Pfeifer http://marc.info/?l=linux-netdev&m=132215646820338&w=2. You could ping him, and try to get his input/Acked-by on your patch. I only did some bug fixing in 3.8 http://marc.info/?l=linux-netdev&m=135897762224399&w=2. Best regards, Johannes --