Patch to add burst to dummynet ?

[Donald Baud]

--- Luigi Rizzo <rizzo at icir.org> wrote:

> On Tue, Feb 21, 2006 at 06:12:01AM -0800, Donald
> Baud wrote:
> > Looking back in the mailing archives
>
http://docs.freebsd.org/cgi/getmsg.cgi?fetch=62536+0+archive/2003/freebsd-ipfw/20030907.freebsd-ipfw
> , I found a message saying that it would be trivial
> to add burst support in dummynet.
> > In that message, it says to change in
> ip_dummynet.c :
> > 
> > -       if (len_scaled > q->numbytes )
> > +       if (len_scaled > q->numbytes +
> q->burst_size)
> > 
> > I did that, even tried len_scaled = 0
> > But I don't see any difference after recompiling,
> kldunload/kldload dummynet.
> > 
> > I still get the same throughput with wget
> --progress=dot some_file
> 
> 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




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