Re: [Make-wifi-fast] [PATCH v3 3/6] mac80211: Add airtime accounting and scheduling to TXQs

From: Dave Taht <dave.taht@gmail.com>
To: Ben Greear <greearb@candelatech.com>
Cc: "Toke Høiland-Jørgensen" <toke@toke.dk>,
	"Rajkumar Manoharan" <rmanohar@codeaurora.org>,
	Make-Wifi-fast <make-wifi-fast@lists.bufferbloat.net>,
	"Simon Barber" <simon@superduper.net>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	ath10k <ath10k@lists.infradead.org>,
	"Felix Fietkau" <nbd@nbd.name>
Subject: Re: [Make-wifi-fast] [PATCH v3 3/6] mac80211: Add airtime accounting and scheduling to TXQs
Date: Mon, 19 Nov 2018 16:37:34 -0800	[thread overview]
Message-ID: <CAA93jw55KywLAMEo=hHcqGdB1-qV3-3CCQe+T6GMNZwR6kRhJw@mail.gmail.com> (raw)
In-Reply-To: <6beaeb84-b705-335b-93a7-36176495099b@candelatech.com>

On Mon, Nov 19, 2018 at 4:20 PM Ben Greear <greearb@candelatech.com> wrote:
>
> On 11/19/2018 04:13 PM, Dave Taht wrote:
> > On Mon, Nov 19, 2018 at 3:56 PM Ben Greear <greearb@candelatech.com> wrote:
> >>
> >> On 11/19/2018 03:47 PM, Dave Taht wrote:
> >>> On Mon, Nov 19, 2018 at 3:30 PM Simon Barber <simon@superduper.net> wrote:
> >>>>
> >>>>
> >>>>
> >>>> On Nov 19, 2018, at 2:44 PM, Toke Høiland-Jørgensen <toke@toke.dk> wrote:
> >>>>
> >>>> Dave Taht <dave@taht.net> writes:
> >>>>
> >>>> Toke Høiland-Jørgensen <toke@toke.dk> writes:
> >>>>
> >>>> Felix Fietkau <nbd@nbd.name> writes:
> >>>>
> >>>> On 2018-11-14 18:40, Toke Høiland-Jørgensen wrote:
> >>>>
> >>>> This part doesn't really make much sense to me, but maybe I'm
> >>>> misunderstanding how the code works.
> >>>> Let's assume we have a driver like ath9k or mt76, which tries to keep a
> >>>>
> >>>> ….
> >>>>
> >>>>
> >>>> Well, there's going to be a BQL-like queue limit (but for airtime) on
> >>>> top, which drivers can opt-in to if the hardware has too much queueing.
> >>>>
> >>>>
> >>>> Very happy to read this - I first talked to Dave Taht about the need for Time Queue Limits more than 5 years ago!
> >>>
> >>> Michal faked up a dql estimator 3 (?) years ago. it worked.
> >>>
> >>> http://blog.cerowrt.org/post/dql_on_wifi_2/
> >>>
> >>> As a side note, in *any* real world working mu-mimo situation at any
> >>> scale, on any equipment, does anyone have any stats on how often the
> >>> feature is actually used and useful?
> >>>
> >>> My personal guess, from looking at the standard, was in home
> >>> scenarios, usage would be about... 0, and in a controlled environment
> >>> in a football stadium, quite a lot.
> >>>
> >>> In a office or apartment complex, I figured interference and so forth
> >>> would make it a negative benefit due to retransmits.
> >>>
> >>> I felt when that part of the standard rolled around... that mu-mimo
> >>> was an idea that should never have escaped the lab. I can be convinced
> >>> by data, that we can aim for a higher goal here. But it would be
> >>> comforting to have a measured non-lab, real-world, at real world
> >>> rates, result for it, on some platform, of it actually being useful.
> >>
> >> We're working on building a lab with 20 or 30 mixed 'real' devices
> >> using various different /AC NICs (QCA wave2 on OpenWRT, Fedora, realtek USB 8812au on OpenWRT, Fedora,
> >> and some Intel NICs in NUCs on Windows, and maybe more).  I'm not actually sure if that realtek
> >>   or the NUCs can do MU-MIMO or not, but the QCA NICs will be able to.  It should be at least somewhat similar
> >> to a classroom environment or coffee shop.
> >
> > In the last 3 coffee shops I went to, I could hear over 30 APs on
> > competing SSIDs, running G, N, and AC,
> > occupying every available channel.
>
> I especially like when someone uses channel 3 because, I guess, they
> think it is un-used :)

I think avery actually found a case where that was a benefit, in an
apartment building that had each per-apartment AP
located at exactly the same place on every floor.

I do wish I could go back in time and explain the four colour theorem
to whoever allocated the 2.4ghz wifi band, and then explain even that
was a planar rather than 3D problem.

The 3D coloring problem I visualize as the scene in Aliens 2, where
the monsters just waltz in over the ceiling panels. To me it's an
indelible image kind of superimposed over the interfering waves in the
air, full of gore, goo, and blood...

>
> I'm not sure if this was a fluke or not, but at Starbucks recently I sat outside,
> right next to their window, and could not scan their AP at all.  Previously, I sat
> inside, 3 feet away through the glass, and got great signal.  I wonder what that was
> all about!  Maybe special tinting that blocks RF?  Or just dumb luck of some sort.

Ya know, I could definitely see a market for a material like that! I'd
like it for my car, so bluetooth wouldn't escape.

anyway, just blowing off steam. :) When v4 of this rolls around + BQL?
I can get some results back on it too. One less than perfect option or
the other would be better than continuing to have lousy wifi in all
cases on all platforms.

> Thanks,
> Ben
>
>
> --
> Ben Greear <greearb@candelatech.com>
> Candela Technologies Inc  http://www.candelatech.com
>

-- 

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740