<div dir="ltr"><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Feb 3, 2014 at 9:30 AM, Nicolas KUHN <span dir="ltr"><<a href="mailto:nicolas.kuhn@telecom-bretagne.eu" target="_blank">nicolas.kuhn@telecom-bretagne.eu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">Dear all,<br>
<br>
We would like to test FQ_CoDel and we wonder which version to evaluate.</blockquote><div><br></div><div class="gmail_default" style="font-size:small">fq_codel has been in Linux since about Linux 3.5, IIRC. For casual experiments, a current Linux distro will have it available at the invocation of the "tc" command. But...</div>
<div><br></div><div class="gmail_default" style="font-size:small">You should generally be testing the latest Linux release (not that I think there has been much change in fq_codel, as demonstrated in: <a href="https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/log/?id=refs%2Ftags%2Fv3.14-rc1&qt=grep&q=fq_codel">https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/log/?id=refs%2Ftags%2Fv3.14-rc1&qt=grep&q=fq_codel</a></div>
<div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">For serious bench marking getting results from an old system can make your results easily invalid since there has been a large number of improvements in Linux for bufferbloat everywhere over the last three years, and the queue discipline is only part of the equation. For example, many ethernet drivers in SOC's found in home routers may still lack even BQL support.</div>
<div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">You should be testing the fq_codel queue discipline: while Dave Taht has played with a number of variants on that theme, nothing to date has shown itself (by testing) with enough better results to be worth merging upstream into <a href="http://kernel.org">kernel.org</a>. Pie finally entered <a href="http://kernel.org">kernel.org</a> Linux a month or so ago.</div>
<div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">Note that there a large number of "traps" for the unwary in this benchmarking/testing business, into which multiple groups have come to bad ends causing questionable results to confuse everyone. For example, the details of the underlying device driver can matter a lot (actually, hugely!), and netem has to be used with exquisite care just to name a couple of the big traps. </div>
<div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">Fundamentally, you need to realize that the queue discipline in Linux (where you can apply aqm) does *not* have control of all of the buffering in the system; device drivers and even the hardware itself can do "interesting" things to you. And a bunch of changes have taken place in the Linux TCP stack to remove unneeded buffering since around Linux 3.2. At one point I think the list was up to a dozen or more significant improvements in the Linux networking stack, independent of fq_codel.</div>
<div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">We've come to learn that WiFi in particular needs a serious rewrite, and before venturing far, you'd be wise to get in touch with us further. ATM, the ath9k driver is least problematic, but even there, aggregation causes large amounts of buffering (32 packets!).</div>
<div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">Dave Taht and I tried to outline what you should be thinking about when bench marking in:</div><div class="gmail_default" style="font-size:small">
<br></div><div class="gmail_default"><a href="http://www.bufferbloat.net/projects/codel/wiki/Best_practices_for_benchmarking_Codel_and_FQ_Codel">http://www.bufferbloat.net/projects/codel/wiki/Best_practices_for_benchmarking_Codel_and_FQ_Codel</a></div>
<div class="gmail_default"><br></div><div class="gmail_default">Pretty much all of these issues apply to anything you do, not just fq_codel.</div><div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">
I think that page overs most of the problems though of course, Linux is a moving target so I'm sure there will be future problems :-(.</div><div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">
<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<br>
Does anyone know where we could get the "official" version / source code of FQ_CoDel ?<br>
(linux and/or NS2 if possible)<br></blockquote><div><br></div><div class="gmail_default" style="font-size:small">www.<a href="http://kernel.org">kernel.org</a> for the source.</div><div class="gmail_default" style="font-size:small">
<br></div><div class="gmail_default" style="font-size:small">You can use git to see the exact revision history of the code.</div><div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">
I forget off hand where to find the simulation code... There is a link somewhere in the bufferbloat/codel wiki</div><div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default"><a href="http://www.bufferbloat.net/projects/codel/wiki/Wiki">http://www.bufferbloat.net/projects/codel/wiki/Wiki</a><br>
</div><div class="gmail_default"><br></div><div class="gmail_default">Help from people to get the wiki up to date gratefully appreciated!</div><div class="gmail_default"><br></div><div class="gmail_default">Jim</div><div class="gmail_default">
<br></div><div class="gmail_default" style="font-size:small"><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<br>
Thanks a lot,<br>
<br>
Kind regards,<br>
<br>
Nicolas<br>
<br>
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