From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ariane Keller Subject: Re: [PATCH 0/2] netem: trace enhancement Date: Sun, 23 Dec 2007 20:54:24 +0100 Message-ID: <476EBCF0.3040507@ee.ethz.ch> References: <20071120231131.oqn4s5eda84k4csw@email.ee.ethz.ch> <474C2246.50205@ee.ethz.ch> <20071129134554.5c25a891@freepuppy.rosehill> <474F3719.30101@trash.net> <47503971.9080509@ee.ethz.ch> <4753B423.7030000@trash.net> <4753C874.80703@ee.ethz.ch> <47543E65.4060303@trash.net> <47544B1F.1010902@candelatech.com> <20071204154535.4eu35nfe9wks8kgg@email.ee.ethz.ch> <47559119.6070803@candelatech.com> <47559455.1080009@ee.ethz.ch> <47559763.9050408@candelatech.com> <4755C984.70906@ee.ethz.ch> <4755D2EB.4000807@candelatech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Ariane Keller , Patrick McHardy , Stephen Hemminger , netdev@vger.kernel.org, Rainer Baumann To: Ben Greear Return-path: Received: from smtp.ee.ethz.ch ([129.132.2.219]:39051 "EHLO smtp.ee.ethz.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751360AbXLWTyf (ORCPT ); Sun, 23 Dec 2007 14:54:35 -0500 In-Reply-To: <4755D2EB.4000807@candelatech.com> Sender: netdev-owner@vger.kernel.org List-ID: I have added the possibility to configure the number of buffers used to store the trace data for packet delays. The complete command to start netem with a trace file is: tc qdisc add dev eth1 root netem trace path/to/trace/file.bin buf 3 loops 1 0 with buf: the number of buffers to be used loops: how many times to loop through the tracefile the last argument is optional and specifies whether the default is to drop packets or 0-delay them. The patches are available at: http://www.tcn.hypert.net/tcn_kernel_2_6_23_confbuf http://www.tcn.hypert.net/tcn_iproute2_2_6_23_confbuf I'm looking forward for your comments! Thanks! Ariane Ben Greear wrote: > Ariane Keller wrote: > >> Yes, for short-term starvation it helps certainly. >> But I'm still not convinced that it is really necessary to add more >> buffers, because I'm not sure whether the bottleneck is really the >> loading of data from user space to kernel space. >> Some basic tests have shown that the kernel starts loosing packets at >> approximately the same packet rate regardless whether we use netem, or >> netem with the trace extension. >> But if you have contrary experience I'm happy to add a parameter which >> defines the number of buffers. > > I have no numbers, so if you think it works, then that is fine with me. > > If you actually run out of the trace buffers, do you just continue to > run with the last settings? If so, that would keep up throughput > even if you are out of trace buffers... > > What rates do you see, btw? (pps, bps). > > Thanks, > Ben > -- Ariane Keller Communication Systems Research Group, ETH Zurich Web: http://www.csg.ethz.ch/people/arkeller Office: ETZ G 60.1, Gloriastrasse 35, 8092 Zurich