[Cerowrt-devel] FQ_Codel lwn draft article review

[Paul E. McKenney]

On Mon, Dec 03, 2012 at 12:31:30PM +0100, Dave Taht wrote:
> 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

Good catch, fixed!

							Thanx, Paul

> 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
>