[Cerowrt-devel] Google working on experimental 3.8 Linux kernel for Android

Dave Taht dave.taht at gmail.com
Thu Feb 28 14:08:50 EST 2013

On Thu, Feb 28, 2013 at 1:57 PM, <dpreed at reed.com> wrote:

> Doesn't fq_codel need an estimate of link capacity?

No, it just measures delay. Since so far as I know the outgoing portion of
LTE is not soft-rate limited, but sensitive to the actual available link
bandwidth, fq_codel should work pretty good (if the underlying interfaces
weren't horribly overbuffired) in that direction.

I'm looking forward to some measurements of actual buffering at the device
driver/device levels.

I don't know how inbound to the handset is managed via LTE.

Still quite a few assumptions left to smash in the above.


in the home router case....


When there are artificial rate limits in play (in, for example, a cable
modem/CMTS, hooked up via gigE yet rate limiting to 24up/4mbit down), then
a rate limiter (tbf,htb,hfsc) needs to be applied locally to move that rate
limiter/queue management into the local device, se we can manage it better.

I'd like to be rid of the need to use htb and come up with a rate limiter
that could be adjusted dynamically from a daemon in userspace, probing for
short all bandwidth fluctuations while monitoring the load. It needent send
that much data very often, to come up with a stable result....

You've described one soft-rate sensing scheme (piggybacking on TCP), and
I've thought up a few others, that could feed back from a daemon some
samples into a a soft(er) rate limiter that would keep control of the
queues in the home router. I am thinking it's going to take way too long to
fix the CPE and far easier to fix the home router via this method, and
certainly it's too painful and inaccurate to merely measure the bandwidth
once, then set a hard rate, when

So far as I know the gargoyle project was experimenting with this approach.

A problem is in places that connect more than one device to the cable
modem... then you end up with those needing to communicate their perception
of the actual bandwidth beyond the link.

Where will it get that from the 4G or 3G uplink?
> -----Original Message-----
> From: "Maciej Soltysiak" <maciej at soltysiak.com>
> Sent: Thursday, February 28, 2013 1:03pm
> To: cerowrt-devel at lists.bufferbloat.net
> Subject: [Cerowrt-devel] Google working on experimental 3.8 Linux kernel
> for Android
>  Hiya,
>  Looks like Google's experimenting with 3.8 for Android:
> https://android.googlesource.com/kernel/common/+/experimental/android-3.8
> Sounds great if this means they will utilize fq_codel, TFO, BQL, etc.
>  Anyway my nexus 7 says it has 3.1.10 and this 3.8 will probably go to
> Android 5.0 so I hope Nexus 7 will get it too some day or at least 3.3+
>  Phoronix coverage:
> http://www.phoronix.com/scan.php?page=news_item&px=MTMxMzc
> Their 3.8 changelog:
> https://android.googlesource.com/kernel/common/+log/experimental/android-3.8
>  Regards,
> Maciej
> _______________________________________________
> Cerowrt-devel mailing list
> Cerowrt-devel at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/cerowrt-devel

Dave Täht

Fixing bufferbloat with cerowrt:
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