[Cake] Cake in mac80211

[Cake] Cake in mac80211

[Bjørn Ivar Teigen]

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Hi,

Are there any plans, work or just comments on the idea of implementing cake
in mac80211 as was done with fq_codel?

-- 
Bjørn Ivar Teigen
Head of Research
Domos, Machine Learning for the Home
www.domos.no

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Re: [Cake] Cake in mac80211

[Jonathan Morton]

> On 4 Feb, 2020, at 5:20 pm, Bjørn Ivar Teigen <bjorn@domos.no> wrote:
> 
> Are there any plans, work or just comments on the idea of implementing cake in mac80211 as was done with fq_codel?

To consider doing that, there'd have to be a concrete benefit to doing so.  Most of Cake's most useful features, beyond what fq_codel already supports, are actually implied or even done better by the WiFi environment and the mac80211 layer adaptation (particularly airtime fairness).

You can of course attach a Cake instance to the wifi interface as well, if you have a need to do so.

 - Jonathan Morton

Re: [Cake] Cake in mac80211

[Dave Taht]

On Tue, Feb 4, 2020 at 7:25 AM Jonathan Morton <chromatix99@gmail.com> wrote:
>
> > On 4 Feb, 2020, at 5:20 pm, Bjørn Ivar Teigen <bjorn@domos.no> wrote:
> >
> > Are there any plans, work or just comments on the idea of implementing cake in mac80211 as was done with fq_codel?
>
> To consider doing that, there'd have to be a concrete benefit to doing so.

Research is research! :) Everything is worth trying! There's got to be
some better ideas out there, and we have a long list of things we
could have done to keep improving wifi had funding not run out.

We barely scratched the surface of this list.

https://docs.google.com/document/d/1Se36svYE1Uzpppe1HWnEyat_sAGghB3kE285LElJBW4/edit

> Most of Cake's most useful features, beyond what fq_codel already supports, are actually implied or even done better by the WiFi environment and the mac80211 layer adaptation (particularly airtime fairness).

In my opinion(s)

A) I think ack-filtering will help somewhat on 802.11n, but it's not
worth the added cpu cost on an AP and I'd prefer hosts reduce their
ack load in the tcp stack (IMHO, others may differ, it's worth trying)
B) The underlying wifi scheduler essentially does per host fq better
than cake can (because it's layer 2 vs layer 3), as per jonathan's
comment above
C) Instead of using a 8 way set associative hash and 1024 queues,
fq_codel for wifi uses 4096 with a disambiguation pointer for
collisions. Seems good enough.
D) "cobalt" is proving out better in several respects than pure codel,
and folding in some of that makes sense, except I don't know which
things are the most valuable considering wifi's other problems
E) I'd like to dynamically increase the quantum size as a function of
load or number of flows.


I'd really like benchmarks of the proprietary versions coming out.
Qualcomm has their own fq_codelish thing baked into their firmware
now... I have no idea what broadcom is doing... fq-pie?

The librerouter is now available. I'd like to try that.

Recently I benchmarked red rock cafe in mountain view, which had the
best bufferbloat and rrul score of any cybercafe I'd ever tried - they
have a mojo networks AP, which arista bought a while back. It was
lovely.... I have no idea what they do,
but whatever it was it was *good*. I'm really happy see bufferbloat
getting fixes everywhere, but really need to add quic to the benchmark
suite somehow in order to feel better about people not rewriring tcp
headers to do what they want.

more importantly:

Would really like to get cracking on a wifi 6 version. So far, all the
vendors are lying, there is no OFDMA support in anything we've played
with. There are some new outer limits there (1000+ devices), a need to
do gang scheduling, and per-station firmware, and I'm
profoundly unimpressed with proprietary vendor's efforts so far and
wish they'd open up their firmware more so more of us could take a
crack at it....

I'd really like to get the intel  (iwl) version, especially the ax200
chips, ported over to the AQL + fq_codel interfaces, at least.  The
first attempt went badly, last quarter. Needs eyeballs and time...
Would like to find some other wifi chip worth fixing - raspi 4? Some
android wifi chip? what?
Don't know how the ath11k effort is going...

In mainline...
 I'd like to get the wifi codel target on 5ghz down from 20ms (too
much) to 10ms, (or as I run it here to 8ms) in mainline, or at least
openwrt, but that would require some benchmarking by multiple folk,
and I was waiting for the ath10k ATF code to go upstream first. At
least make it tunable.

Overall, reducing hw retries to sanity would be a nice thing to
attempt in the ath9k, at least. Although the ongoing SCE work (gradual
rate reduction) is interesting, I tend to think reducing hardware
retries (with increased loss) would have a more dramatic effect on
reducing wifi latencies.
Presently with the codel target of 20ms in both directions, I get
60-80ms tcp latencies (still better than most fiber!) over wifi with a
20ms target at 70mbits. What happens at 300+, no idea. cynically I
think much of the internet is essentially running at a max rwind or
swind rather than within athe sawtooth.

doing something more sane to rate limit multicast would be good also.
It was quite the long list in that google document, back in the day we
thought the wifi industry might decide to collaborate in order to meet
the 5G threat.

> a Cake instance to the wifi interface as well, if you have a need to do so.

It certainly is feasible to do that. I do that now on several 802.11ac
devices that don't have the fq_codel for wifi hooks, preferring to
rate limit them well below capacity so as to ensure consistent low
latency. It's really neat to see people able to play world of warcraft
and other games over
the wifi here. ( started deploying ubnt's uap mesh products, reflashed
with openwrt, along portions of my wifi backbone . Looking forward to
the AQL backport for those, but I hope someone else does it)

>
>  - Jonathan Morton
> _______________________________________________
> Cake mailing list
> Cake@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/cake



-- 
Make Music, Not War

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-435-0729

Re: [Cake] Cake in mac80211

[Bjørn Ivar Teigen]

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Thanks for the feedback!

Some comments and questions added inline.

On Tue, 4 Feb 2020 at 18:07, Dave Taht <dave.taht@gmail.com> wrote:

> On Tue, Feb 4, 2020 at 7:25 AM Jonathan Morton <chromatix99@gmail.com>
> wrote:
> >
> > > On 4 Feb, 2020, at 5:20 pm, Bjørn Ivar Teigen <bjorn@domos.no> wrote:
> > >
> > > Are there any plans, work or just comments on the idea of implementing
> cake in mac80211 as was done with fq_codel?
> >
> > To consider doing that, there'd have to be a concrete benefit to doing
> so.
>
> Research is research! :) Everything is worth trying! There's got to be
> some better ideas out there, and we have a long list of things we
> could have done to keep improving wifi had funding not run out.
>
> We barely scratched the surface of this list.
>
>
> https://docs.google.com/document/d/1Se36svYE1Uzpppe1HWnEyat_sAGghB3kE285LElJBW4/edit
>
> > Most of Cake's most useful features, beyond what fq_codel already
> supports, are actually implied or even done better by the WiFi environment
> and the mac80211 layer adaptation (particularly airtime fairness).
>
> In my opinion(s)
>
> A) I think ack-filtering will help somewhat on 802.11n, but it's not
> worth the added cpu cost on an AP and I'd prefer hosts reduce their
> ack load in the tcp stack (IMHO, others may differ, it's worth trying)
> B) The underlying wifi scheduler essentially does per host fq better
> than cake can (because it's layer 2 vs layer 3), as per jonathan's
> comment above

C) Instead of using a 8 way set associative hash and 1024 queues,
> fq_codel for wifi uses 4096 with a disambiguation pointer for
> collisions. Seems good enough.
>

Didn't catch that before. Are the extra queues there because of the
different access categories on Wi-Fi? Seems like that would mean most of
them are not in use considering how little traffic is marked with DSCP.

D) "cobalt" is proving out better in several respects than pure codel,
> and folding in some of that makes sense, except I don't know which
> things are the most valuable considering wifi's other problems
>

Reading paper now. Thanks for the pointer.


> E) I'd like to dynamically increase the quantum size as a function of
> load or number of flows.
>

>
> I'd really like benchmarks of the proprietary versions coming out.
> Qualcomm has their own fq_codelish thing baked into their firmware
> now... I have no idea what broadcom is doing... fq-pie?
>

I've started looking at benchmarking proprietary drivers with emphasis on
queueing performance. If you have any tips, or if you would like to
co-author a paper (I'm working on a PhD), I am very interested.


>
> The librerouter is now available. I'd like to try that.
>
> Recently I benchmarked red rock cafe in mountain view, which had the
> best bufferbloat and rrul score of any cybercafe I'd ever tried - they
> have a mojo networks AP, which arista bought a while back. It was
> lovely.... I have no idea what they do,
> but whatever it was it was *good*. I'm really happy see bufferbloat
> getting fixes everywhere, but really need to add quic to the benchmark
> suite somehow in order to feel better about people not rewriring tcp
> headers to do what they want.
>
> more importantly:
>
> Would really like to get cracking on a wifi 6 version. So far, all the
> vendors are lying, there is no OFDMA support in anything we've played
> with. There are some new outer limits there (1000+ devices), a need to
> do gang scheduling, and per-station firmware, and I'm
> profoundly unimpressed with proprietary vendor's efforts so far and
> wish they'd open up their firmware more so more of us could take a
> crack at it....
>

I agree, there are some interesting problems arising there. Interested to
follow the work if and when this happens. Any luck finding a company
willing to work on open-source drivers for Wi-Fi 6?


> I'd really like to get the intel  (iwl) version, especially the ax200
> chips, ported over to the AQL + fq_codel interfaces, at least.  The
> first attempt went badly, last quarter. Needs eyeballs and time...
> Would like to find some other wifi chip worth fixing - raspi 4? Some
> android wifi chip? what?
> Don't know how the ath11k effort is going...
>
> In mainline...
>  I'd like to get the wifi codel target on 5ghz down from 20ms (too
> much) to 10ms, (or as I run it here to 8ms) in mainline, or at least
> openwrt, but that would require some benchmarking by multiple folk,
> and I was waiting for the ath10k ATF code to go upstream first. At
> least make it tunable.
>

Have done some testing myself and 10ms looks like the correct limit on 5GHz.


>
> Overall, reducing hw retries to sanity would be a nice thing to
> attempt in the ath9k, at least. Although the ongoing SCE work (gradual
> rate reduction) is interesting, I tend to think reducing hardware
> retries (with increased loss) would have a more dramatic effect on
> reducing wifi latencies.
> Presently with the codel target of 20ms in both directions, I get
> 60-80ms tcp latencies (still better than most fiber!) over wifi with a
> 20ms target at 70mbits. What happens at 300+, no idea. cynically I
> think much of the internet is essentially running at a max rwind or
> swind rather than within athe sawtooth.
>

Also interesting


>
> doing something more sane to rate limit multicast would be good also.
> It was quite the long list in that google document, back in the day we
> thought the wifi industry might decide to collaborate in order to meet
> the 5G threat.
>
> > a Cake instance to the wifi interface as well, if you have a need to do
> so.
>
> It certainly is feasible to do that. I do that now on several 802.11ac
> devices that don't have the fq_codel for wifi hooks, preferring to
> rate limit them well below capacity so as to ensure consistent low
> latency. It's really neat to see people able to play world of warcraft
> and other games over
> the wifi here. ( started deploying ubnt's uap mesh products, reflashed
> with openwrt, along portions of my wifi backbone . Looking forward to
> the AQL backport for those, but I hope someone else does it)
>

Have this setup at home and it really does make a difference, even with
just normal browsing. Has bigger impact than I would have guessed!

>
> >
> >  - Jonathan Morton
> > _______________________________________________
> > Cake mailing list
> > Cake@lists.bufferbloat.net
> > https://lists.bufferbloat.net/listinfo/cake
>
>
>
> --
> Make Music, Not War
>
> Dave Täht
> CTO, TekLibre, LLC
> http://www.teklibre.com
> Tel: 1-831-435-0729
>


-- 
Bjørn Ivar Teigen
Head of Research
Domos, Machine Learning for the Home
www.domos.no

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Re: [Cake] Cake in mac80211

[Dave Taht]

Bjørn Ivar Teigen <bjorn@domos.no> writes:

> Thanks for the feedback!
>
> Some comments and questions added inline.
>
> On Tue, 4 Feb 2020 at 18:07, Dave Taht <dave.taht@gmail.com> wrote:
>
>     On Tue, Feb 4, 2020 at 7:25 AM Jonathan Morton
>     <chromatix99@gmail.com> wrote:
>     >
>     > > On 4 Feb, 2020, at 5:20 pm, Bjørn Ivar Teigen <bjorn@domos.no>
>     wrote:
>     > >
>     > > Are there any plans, work or just comments on the idea of
>     implementing cake in mac80211 as was done with fq_codel?
>     >
>     > To consider doing that, there'd have to be a concrete benefit to
>     doing so.
>     
>     Research is research! :) Everything is worth trying! There's got
>     to be
>     some better ideas out there, and we have a long list of things we
>     could have done to keep improving wifi had funding not run out.
>     
>     We barely scratched the surface of this list.
>     
>     https://docs.google.com/document/d/1Se36svYE1Uzpppe1HWnEyat_sAGghB3kE285LElJBW4/edit
>    
>     
>     > Most of Cake's most useful features, beyond what fq_codel
>     already supports, are actually implied or even done better by the
>     WiFi environment and the mac80211 layer adaptation (particularly
>     airtime fairness).
>     
>     In my opinion(s)
>     
>     A) I think ack-filtering will help somewhat on 802.11n, but it's
>     not
>     worth the added cpu cost on an AP and I'd prefer hosts reduce
>     their
>     ack load in the tcp stack (IMHO, others may differ, it's worth
>     trying)
>     B) The underlying wifi scheduler essentially does per host fq
>     better
>     than cake can (because it's layer 2 vs layer 3), as per jonathan's
>     comment above 
>
>     C) Instead of using a 8 way set associative hash and 1024 queues,
>     fq_codel for wifi uses 4096 with a disambiguation pointer for
>     collisions. Seems good enough.
>     
>
> Didn't catch that before. Are the extra queues there because of the
> different access categories on Wi-Fi? Seems like that would mean most
> of them are not in use considering how little traffic is marked with
> DSCP.

I wasn't counting those. There's one set of 4k queues per access class.

While I agree that access classes are rarely used, and am of the opinion
that they shouldn't actually be used on an n or ac AP as better scheduling of the
BE class suffices. 802.11e is useful on well behaved clients for a few
things.

the number of queues was kind of picked as a function of the absolute maximum
number of stations wireless-n can take and a swag.

our original conception was that we'd have one fairly small fq_codel
instance per station, dynamically arriving and departing as the station
did, which proved really problematic to implement - we were stuck on how
stateful it was and all kinds of locking issues, for nearly 2 years
before michiel kazior came up with the simpler "lots of queues +
disambiguation pointer" idea.

Another idea unexplored is clamping the used and advertised (in the
beacon) txop size dynamically when under higher contention. I certainly
get better latency with a 2-3ms txop, but I never got around to
publishing those results in a coherent form. it also increases the
opportunities for an effective mu-mimo burst.

This to me is way better than explicitly choosing access classes.

My take on things for wifi 6 was that firmware needed to expose a per
station abstraction, and we needed to go back to the fq_codel instance
per station idea.

>
>     D) "cobalt" is proving out better in several respects than pure
>     codel,
>     and folding in some of that makes sense, except I don't know which
>     things are the most valuable considering wifi's other problems
>     
>
> Reading paper now. Thanks for the pointer.

I tend to think out that fq_codel is "good enough" in most
circumstances. The edge cases that cake handles better are a matter of a
few percentage points, vs orders of magnitude that we get with fq_codel
alone vs a vs a FIFO, and my focus of late has been to make things that
ate less cpu or were better offloadable than networked better. Others differ. 


>     E) I'd like to dynamically increase the quantum size as a function
>     of
>     load or number of flows. 
>     
>
>     I'd really like benchmarks of the proprietary versions coming out.
>     Qualcomm has their own fq_codelish thing baked into their firmware
>     now... I have no idea what broadcom is doing... fq-pie?
>     
>
> I've started looking at benchmarking proprietary drivers with emphasis
> on queueing performance. If you have any tips,

I've been after eero in particular to publish results.

> or if you would like to
> co-author a paper (I'm working on a PhD), I am very interested.

I have been without a voice since toke graduated, so yes.

>
>     The librerouter is now available. I'd like to try that.
>     
>     Recently I benchmarked red rock cafe in mountain view, which had
>     the
>     best bufferbloat and rrul score of any cybercafe I'd ever tried -
>     they
>     have a mojo networks AP, which arista bought a while back. It was
>     lovely.... I have no idea what they do,
>     but whatever it was it was *good*. I'm really happy see
>     bufferbloat
>     getting fixes everywhere, but really need to add quic to the
>     benchmark
>     suite somehow in order to feel better about people not rewriring
>     tcp
>     headers to do what they want.
>     
>     more importantly:
>     
>     Would really like to get cracking on a wifi 6 version. So far, all
>     the
>     vendors are lying, there is no OFDMA support in anything we've
>     played
>     with. There are some new outer limits there (1000+ devices), a
>     need to
>     do gang scheduling, and per-station firmware, and I'm
>     profoundly unimpressed with proprietary vendor's efforts so far
>     and
>     wish they'd open up their firmware more so more of us could take a
>     crack at it....
>     
>
> I agree, there are some interesting problems arising there. Interested
> to follow the work if and when this happens. Any luck finding a
> company willing to work on open-source drivers for Wi-Fi 6?

Nope. Feel free to try harder! I keep thinking that with various parties
struggling so hard they might actually try to open things up...

>     I'd really like to get the intel (iwl) version, especially the
>     ax200
>     chips, ported over to the AQL + fq_codel interfaces, at least. The
>     first attempt went badly, last quarter. Needs eyeballs and time...
>     Would like to find some other wifi chip worth fixing - raspi 4?
>     Some
>     android wifi chip? what?
>     Don't know how the ath11k effort is going...
>     
>     In mainline...
>     I'd like to get the wifi codel target on 5ghz down from 20ms (too
>     much) to 10ms, (or as I run it here to 8ms) in mainline, or at
>     least
>     openwrt, but that would require some benchmarking by multiple
>     folk,
>     and I was waiting for the ath10k ATF code to go upstream first. At
>     least make it tunable.
>     
>
> Have done some testing myself and 10ms looks like the correct limit on
> 5GHz.

Yea! Put results somewhere... I've kind of made a mistake in that I
ran my own patched kernels and openwrt instances for years now and
didn't really notice what hadn't got done until some testing at the last
battlemesh. Getting AQL for ath10k upstream is one piece of fallout from that.


>     Overall, reducing hw retries to sanity would be a nice thing to
>     attempt in the ath9k, at least. Although the ongoing SCE work
>     (gradual
>     rate reduction) is interesting, I tend to think reducing hardware
>     retries (with increased loss) would have a more dramatic effect on
>     reducing wifi latencies.
>     Presently with the codel target of 20ms in both directions, I get
>     60-80ms tcp latencies (still better than most fiber!) over wifi
>     with a
>     20ms target at 70mbits. What happens at 300+, no idea. cynically I
>     think much of the internet is essentially running at a max rwind
>     or
>     swind rather than within athe sawtooth.
>     
>
> Also interesting
>
>     doing something more sane to rate limit multicast would be good
>     also.
>     It was quite the long list in that google document, back in the
>     day we
>     thought the wifi industry might decide to collaborate in order to
>     meet
>     the 5G threat.
>     
>     > a Cake instance to the wifi interface as well, if you have a
>     need to do so.
>     
>     It certainly is feasible to do that. I do that now on several
>     802.11ac
>     devices that don't have the fq_codel for wifi hooks, preferring to
>     rate limit them well below capacity so as to ensure consistent low
>     latency. It's really neat to see people able to play world of
>     warcraft
>     and other games over
>     the wifi here. ( started deploying ubnt's uap mesh products,
>     reflashed
>     with openwrt, along portions of my wifi backbone . Looking forward
>     to
>     the AQL backport for those, but I hope someone else does it)
>     
>
> Have this setup at home and it really does make a difference, even
> with just normal browsing. Has bigger impact than I would have
> guessed!

Normal browsing rocks on fq_codel derived solutions.

See fig 14 and fig 24 on this cablelabs study

https://www-res.cablelabs.com/wp-content/uploads/2019/02/28094118/Active_Queue_Management_Algorithms_DOCSIS_3_0.pdf

Why pie "won" to this day bothers me, as at the time it seemed feasible
to implement fq_codel decently on this class of devices. 

(and they weren't even benchmarking the final fq_codel version, but a
quite crippled sfq based one)

>
>     >
>     > - Jonathan Morton
>     > _______________________________________________
>     > Cake mailing list
>     > Cake@lists.bufferbloat.net
>     > https://lists.bufferbloat.net/listinfo/cake
>     
>     
>     
>     -- 
>     Make Music, Not War
>     
>     Dave Täht
>     CTO, TekLibre, LLC
>     http://www.teklibre.com
>     Tel: 1-831-435-0729

Re: [Cake] [Make-wifi-fast] Cake in mac80211

[Toke Høiland-Jørgensen]

Dave Taht <dave@taht.net> writes:

> Bjørn Ivar Teigen <bjorn@domos.no> writes:
>
>> Thanks for the feedback!
>>
>> Some comments and questions added inline.
>>
>> On Tue, 4 Feb 2020 at 18:07, Dave Taht <dave.taht@gmail.com> wrote:
>>
>>     On Tue, Feb 4, 2020 at 7:25 AM Jonathan Morton
>>     <chromatix99@gmail.com> wrote:
>>     >
>>     > > On 4 Feb, 2020, at 5:20 pm, Bjørn Ivar Teigen <bjorn@domos.no>
>>     wrote:
>>     > >
>>     > > Are there any plans, work or just comments on the idea of
>>     implementing cake in mac80211 as was done with fq_codel?
>>     >
>>     > To consider doing that, there'd have to be a concrete benefit to
>>     doing so.
>>     
>>     Research is research! :) Everything is worth trying! There's got
>>     to be
>>     some better ideas out there, and we have a long list of things we
>>     could have done to keep improving wifi had funding not run out.
>>     
>>     We barely scratched the surface of this list.
>>     
>>     https://docs.google.com/document/d/1Se36svYE1Uzpppe1HWnEyat_sAGghB3kE285LElJBW4/edit
>>    
>>     
>>     > Most of Cake's most useful features, beyond what fq_codel
>>     already supports, are actually implied or even done better by the
>>     WiFi environment and the mac80211 layer adaptation (particularly
>>     airtime fairness).
>>     
>>     In my opinion(s)
>>     
>>     A) I think ack-filtering will help somewhat on 802.11n, but it's
>>     not
>>     worth the added cpu cost on an AP and I'd prefer hosts reduce
>>     their
>>     ack load in the tcp stack (IMHO, others may differ, it's worth
>>     trying)
>>     B) The underlying wifi scheduler essentially does per host fq
>>     better
>>     than cake can (because it's layer 2 vs layer 3), as per jonathan's
>>     comment above 
>>
>>     C) Instead of using a 8 way set associative hash and 1024 queues,
>>     fq_codel for wifi uses 4096 with a disambiguation pointer for
>>     collisions. Seems good enough.
>>     
>>
>> Didn't catch that before. Are the extra queues there because of the
>> different access categories on Wi-Fi? Seems like that would mean most
>> of them are not in use considering how little traffic is marked with
>> DSCP.
>
> I wasn't counting those. There's one set of 4k queues per access
> class.

Nit: not per access class; they're shared across the whole phy.

-Toke

Re: [Cake] [Make-wifi-fast] Cake in mac80211

[Jonathan Morton]

> On 5 Feb, 2020, at 6:06 pm, Dave Taht <dave@taht.net> wrote:
> 
>>    D) "cobalt" is proving out better in several respects than pure
>>    codel,
>>    and folding in some of that makes sense, except I don't know which
>>    things are the most valuable considering wifi's other problems
>> 
>> Reading paper now. Thanks for the pointer.
> 
> I tend to think out that fq_codel is "good enough" in most
> circumstances. The edge cases that cake handles better are a matter of a
> few percentage points, vs orders of magnitude that we get with fq_codel
> alone vs a vs a FIFO, and my focus of late has been to make things that
> ate less cpu or were better offloadable than networked better. Others differ. 

I think COBALT might be worth putting in, as it should have essentially no net cost and does behave a little better than stock Codel.  It's better at handling unresponsive traffic, in particular.

 - Jonathan Morton

Re: [Cake] [Make-wifi-fast] Cake in mac80211

[Dave Taht]

Jonathan Morton <chromatix99@gmail.com> writes:

>> On 5 Feb, 2020, at 6:06 pm, Dave Taht <dave@taht.net> wrote:
>> 
>>>    D) "cobalt" is proving out better in several respects than pure
>>>    codel,
>>>    and folding in some of that makes sense, except I don't know which
>>>    things are the most valuable considering wifi's other problems
>>> 
>>> Reading paper now. Thanks for the pointer.
>> 
>> I tend to think out that fq_codel is "good enough" in most
>> circumstances. The edge cases that cake handles better are a matter of a
>> few percentage points, vs orders of magnitude that we get with fq_codel
>> alone vs a vs a FIFO, and my focus of late has been to make things that
>> ate less cpu or were better offloadable than networked better. Others differ. 
>
> I think COBALT might be worth putting in, as it should have
> essentially no net cost and does behave a little better than stock
> Codel.  It's better at handling unresponsive traffic, in particular.

Cake, as a whole, benchmarks out at 2x+ more cpu than htb + fq_codel
does, while admittedly doing more stuff. 

There are 3 interrelated algorithms in cobalt

1) saturating arithmetic. I have no idea if current compilers do
saturated arith on either mips or arm boxes better than they do, but
intel still doesn't. Hate wasting the cpu on it, and don't mind that the
counter overflows after 4 billion iterations on some workloads.

(I did upstream a mild improvement to the bulk dropper a few months back)

2) Blue - to me - unproven as yet - as I'd like to try saturating
arithmetic.

3) I *LIKE* the more graduated drop off in cobalt... in theory.

...

Also, in the case of wifi, we never implemented the bulk dropper that
the mainline code has, and should definately do that. 

...

4) Increasingly I feel the need to drop unresponsive ecn flows more
robustly. I like what you stuck in your current SCE tree to make blue
kick in earlier. Needs benchmarks...

5) As for things like the invsqrt cache, meh, don't feel like that much
accuracy is required, costs an expensive memory access, wanted to see
how well pie and dualq worked. (Really wish P4 and BPF had an invsqrt
primitive.)

6) Same goes for set associativity.

I LIKE competition! The more folk we have hacking on this stuff the
better it gets. :) I've helped get fq-pie mainlined to have another
reference for comparison, with some hope for seeing more stuff offloaded
on more devices....

But in the scheme of debloating things, and sticking to just wifi for
this paragraph, tend to feel that txop clamping, & reducing hw retries,
and doing saner things with multicast, are a bigger win than
improvements to fq_codel itself or cake.

I haven't done much work on fq_codel_fast of late, but I threw out
everything people didn't use, and put in new things that were needed
like gso splitting and an early version of SCE, but few have tried
it... and my original goal for it was to have a multi-core shaper
facility in it and more limited queues automatically when used as
a default qdisc - 64000 fq_codeld (or cake!) queues seems like quite a
lot when you have 64 hw mqs. I'd be more comfortable if it autotuned...

(see also rss++)

... in terms of fantasizing ...

I'd like cake, to be able to use RSS and shape across
multiple cores. My basic dream has generally been that a single
line for inbound shaping that worked with RSS would work miracles.

tc qdisc add dev eth0 ingress cake 100Mbit.

without needing to use tc mirred.

A lot of good things have happened over the last few years to make that
more feasible - listification as one example. For all I know it's easy
to do now....

Would love to see a hardware offload. Am looking forward to google's
preso on their ebf+etx solution at netdevconf. Might be a game changer,
that... it feeds back into my old concept for the "bobbie" policer
much better if only timestamps worked from hw ingress to hw egress.

e2e: I'd really like to see BBRv1 gain RFC3168 and BBRv2 get SCE for
comparison purposes. I'm looking forward to the preliminary experiments
with mmwave radio (paper upcoming) because I think we're all thinking
about how that's going to work, wrong... 

And I'd like new grant money derived from a penny per user voluntary
donation from the billion+ machines running fq_codel...

And a pony.

It's my hope more people show up to go and explore all these options,
and collaborate and make a better, bufferbloat-free internet, somehow,
in my lifetime.



>
>  - Jonathan Morton

Re: [Cake] Cake in mac80211

[Dave Taht]

btw, I didn't look up what domos.no does until now (everybody take a
look!). ML is interesting. We've really struggled to find ways to
autotune cake properly, in particular. We designed it to be easily
tunable, but how to tune is a black art. I got a kick out of the
"remy" work....