[Cerowrt-devel] FQ_Codel lwn draft article review

[Dave Taht]

On Mon, Dec 3, 2012 at 12:24 PM, Toke Høiland-Jørgensen <toke at toke.dk> wrote:
> "Paul E. McKenney" <paulmck at linux.vnet.ibm.com> writes:
>
>> And please see attached.  Thoughts?
>
>"In addition, you network driver must be instrumented to support packet
^^^^ your ethernet network driver

different technologies have different answers. BQL is an answer to
ethernet. ADSL benefits from closely tieing buffering to being nearly
zero and to signalling the actual packet delivery from the hardware.

Wifi, well, I don't want to talk about wifi...

> scheduling..."
>
> So what happens if you run fq_codel on a non-BQL driver?

you have no control. The tx queue rings are flooded before control is
handed back to the fq_codel scheduler. You can get some control back
on a non-BQL driver by reducing the number of tx descriptors
dramatically, but that leads to issues with small vs big packets....

Be worthwhile to plot BQL vs non-BQL on the same driver/device....

>
> -Toke
>
> --
> Toke Høiland-Jørgensen
> toke at toke.dk



-- 
Dave Täht

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