Patch to add burst to dummynet ?

[Donald Baud]

> On Tue, Feb 21, 2006 at 06:57:10AM -0800, Donald
> Baud wrote:
> > 
> > 
> > --- Luigi Rizzo <rizzo at icir.org> wrote:
> ...
> > > of course you get the same throughput!
> > > the burst is just a constant in the time it
> takes to
> > > transfer data,
> > > and it is independent of the data size.
> irrespective
> > > of the file
> > > size you'll just finish (burst_size/bandwidth)
> > > seconds earlier.
> > > 
> > > cheers
> > > luigi
> > 
> > I ran two tests with the following ipfw rules:
> > ipfw pipe 10 config bw 10kbit/s
> > ipfw add 5 pipe 10 ip from 10.0.0.1 to me
> > == with: if (len_scaled > q->numbytes) ==
> > wget --progress=dot some_file
> >     0K .......... ..........  0%    1.13 KB/s
> >    50K .......... ..........  1%    1.14 KB/s
> >   100K .......... ..........  2%    1.14 KB/s
> >   150K .......... ..........  3%    1.14 KB/s
> > 
> > == with: if (len_scaled > q->numbytes + 100000 )
> > wget --progress=dot some_file
> >     0K .......... ..........  0%    1.13 KB/s
> >    50K .......... ..........  1%    1.14 KB/s
> >   100K .......... ..........  2%    1.14 KB/s
> >   150K .......... ..........  3%    1.14 KB/s

> 
> and so ? as i said, the throughtput is the same, you
> just see things happening a little bit (very little,
> usually) earlier,
> and your experiment has no notion of time, and
> furthermore there are so many factors influencing
> the throughput and the numbers printed by wget
> that it's hard to tell how can you see the
> difference.
> 
> assuming, of course, that the patch i suggested
> works, which i
> think but cannot guarantee.
> 
> cheers
> luigi
> 

Are you saying that wget bandwidth reading is
incorrect? I expected to see full speed of the pipe
for the first 100KBytes.
 
I even commented out:
/*
        if (len_scaled > q->numbytes)
            break ; 
*/
While I would have expected full throughput, I got
only ~10X the speed of the pipe:

    0K .......... ..........  0%    8.30 KB/s
   50K .......... ..........  1%   20.70 KB/s
  100K .......... ..........  2%   13.80 KB/s
  150K .......... ..........  3%   13.80 KB/s


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