Re: [Bloat] [iccrg] ECN support for PIE AQM in Linux

From: Dave Taht <dave.taht@gmail.com>
To: Naeem Khademi <naeem.khademi@gmail.com>
Cc: "iccrg@irtf.org" <iccrg@irtf.org>, "aqm@ietf.org" <aqm@ietf.org>,
	bloat <bloat@lists.bufferbloat.net>
Subject: Re: [Bloat] [iccrg] ECN support for PIE AQM in Linux
Date: Wed, 14 Aug 2013 17:41:59 -0700	[thread overview]
Message-ID: <CAA93jw7Omv-j7u-wHPwyuKN5y-htEr+G248_-4jbZRveOBzwMg@mail.gmail.com> (raw)
In-Reply-To: <CAEjQQ5VXiKTAwCa8jxAdCMxGUcACx1yYomOB4_d6P-pp58vVnQ@mail.gmail.com>

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The pie patches that I was using until recently are here:

http://snapon.lab.bufferbloat.net/~cero2/deb/patches/

Stephen hemminger and I cleaned up the original pie drop according to
KernelStyle in multiple ways. There is a rounding error problem in setting
the target value
(we'd recomended they switch to ktime rather than jiffies) that I either
added or was in there in the first place.... and we fixed a couple generic
bugs...

In addition to adding ecn support, we also added congestion notification to
(a la the linux red and fq_codel algorithms) to provide lossless feedback
into the host tcp stack. (this is, incidentally, 1 line of code) This
optimization made it possible to do comparisons on host <-> host tests
between these qdiscs, with no router in-between.

Syntactically the iproute2 patches could use identical syntax for time
based values as the codel iproute2 patches. Haven't got around to that.
(not my job, really, to improve cisco's code)

Now, I only now - today! - just noticed that the new pie code at cisco's
site seems *substantially* different from the older pie code the above was
based on, in that it no longer has an optimization for not dropping smaller
packets. (bytemode) This is going to invalidate most previous benchmarks of
pie that I know of, including all of mine, and most, if not all, of
cablelabs'. Sigh.

I will try to refresh my patches and update the lab over the next week or
so.

On Wed, Aug 14, 2013 at 2:17 PM, Naeem Khademi <naeem.khademi@gmail.com>wrote:

> Hi Vijay
>
> This code implements basic ECN capability for PIE meaning that it
> would CE-mark packets that would be early-dropped otherwise. I have
> sanity-checked the code (e.g. successful ECN marking and
> receiver/sender reaction). We're now in process of conducting larger
> set of experiments with PIE w/wo ECN that will eventually be published
> as we move forward.
>
> Cheers,
> Naeem
>
> On Wed, Aug 14, 2013 at 8:27 PM, Vijay Subramanian
> <subramanian.vijay@gmail.com> wrote:
> > Naeem,
> >
> > Thanks for testing and the contribution! We have ECN support in our
> current
> > code-under-development thanks to earlier help from Dave Taht but I will
> > merge your changes as appropriate and
> > submit it back for review.
> >
> > I will take a look at your code soon. Do you also have any test results
> > which you can share?
> >
> > Thanks again,
> > Vijay
> >
> >
> > On 14 August 2013 07:05, Naeem Khademi <naeem.khademi@gmail.com> wrote:
> >>
> >> Hi
> >>
> >> The already-existing PIE Linux code maintained at
> >> ftp://ftpeng.cisco.com/pie/ does not support ECN. Studying the
> interaction
> >> of ECN and AQM algos is probably of interest of some of us. I have
> added ECN
> >> support to PIE Linux code and have given it some basic sanity tests.
> >>
> >> The modified code is available at
> >> http://heim.ifi.uio.no/naeemk/research/PIE/
> >>
> >> I would appreciate any feedback.
> >>
> >> Regards,
> >> Naeem
> >>
> >>
> >>
> >> _______________________________________________
> >> iccrg mailing list
> >> iccrg@irtf.org
> >> https://www.irtf.org/mailman/listinfo/iccrg
> >>
> >
> _______________________________________________
> iccrg mailing list
> iccrg@irtf.org
> https://www.irtf.org/mailman/listinfo/iccrg
>

-- 
Dave Täht

Fixing bufferbloat with cerowrt:
http://www.teklibre.com/cerowrt/subscribe.html

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