[Cake] Modification of DRR with deficit saving

[Luca Muscariello]

Sanity check: the active flow list in Jim's work is very compact
as it counts only the flows with a packet in the queue.
So you need to read that paragraph with this in mind. Then you'll agree :)

I have a reasonable proof that what cake is doing is truly sane.
You just need to compare cake to Jim's monumental work and see that it fits
in that class.
Then you sleep well as I do.

don't pay too much attention to admission control.
Even if it makes sense to me. In case of overload, i.e. too many flows in
the system for too long,
nobody is happy.
Accepting more flows is making no one happier. The new one included.
So instead of dropping one random packet, dropping new SYN packets seems
like the bouncer telling
you "guys: there is no room left". And it works well in the home.






On Thu, Jan 4, 2018 at 4:42 PM, Dave Taht <dave.taht at gmail.com> wrote:

> On Thu, Jan 4, 2018 at 7:23 AM, Luca Muscariello
> <luca.muscariello at gmail.com> wrote:
> > I think the closest scheduler to Cake is this one, if I have to compare:
> >
> > https://team.inria.fr/rap/files/2013/12/KOR05.pdf
>
> Try as I might, at workloads that I've been able to create (I did just
> add 10GigE capability to my testbed), it's seemingly nearly impossible
> to have more than a few hundred flows in memory (compared to
> potentially thousands actually active), and it's unclear how to go
> about thinking about it sanely.This tends to point to cake's 8 way set
> associativity as being overkill, but haven't got around to trying
> higher bandwidths, lower target RTTs, or, as I said, higher
> bandwidths.
>
> 'course, while I disagree with this statement in the paper, and do
> care a lot about handling overload sanely,
>
> "In overload, it is necessary to apply per-flow admission control in
> order to preserve good performance for admitted flows. Note that no
> scheduler can avoid drastic performance degradation when offered
> traffic exceeds capacity. PDRR has the advantage of allowing"
>
> I wish I had reasonable proof that what we do in cake is truly sane,
> or had some curve to apply to flows per the available bandwidth.
>
> >
> > J. Roberts et al. Implicit Service Differentiation using Deficit Round
> > Robin, In Proc of ITC 2005.
> >
> > Luca
> >
> >
> > On Thu, Jan 4, 2018 at 4:01 PM, Jonathan Morton <chromatix99 at gmail.com>
> > wrote:
> >>
> >> > On 4 Jan, 2018, at 4:29 pm, Toke Høiland-Jørgensen <toke at toke.dk>
> wrote:
> >> >
> >> > This popped up in my Google Scholar notifications:
> >> >
> >> > https://atlas.informatik.uni-tuebingen.de/~menth/papers/Menth18b.pdf
> >> >
> >> > Basically, they are proposing to permit a queue to accumulate a larger
> >> > deficit while empty to allow light users to achieve the same
> throughput
> >> > as heavy users (users being an endpoint with potentially multiple
> >> > flows).
> >> >
> >> > Not sure how useful this really is, but it's somewhat related to
> Cake's
> >> > src/dst user fairness feature, so may be of interest.
> >>
> >> They're trying to solve the same problem as DRR++ does, not the same one
> >> as Triple Isolation does.
> >>
> >> As a result, they've basically proposed a bugfix to the original DRR
> (ie.
> >> you should keep replenishing the deficit until it saturates, even if the
> >> queue is temporarily empty), without gaining the full benefit of DRR++.
> >>
> >> Not interesting at all.
> >>
> >>  - Jonathan Morton
> >>
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> >> https://lists.bufferbloat.net/listinfo/cake
> >
> >
> >
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> >
>
>
>
> --
>
> Dave Täht
> CEO, TekLibre, LLC
> http://www.teklibre.com
> Tel: 1-669-226-2619
>
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