Patch to add burst to dummynet ?

[Luigi Rizzo]

On Tue, Feb 21, 2006 at 08:37:37AM -0800, Donald Baud wrote:
...
> > if you see just one line above your patch,
> > len_scaled is computed as
> > 
> >         int len_scaled = p->bandwidth ? len*8*hz : 0
> > ;
> > 
> > so your '100000' correspond (with HZ=1000) to an
> > actual burst
> > of 100 bits or 12.5 bytes so hardly measurable.
> > secondly, as i said the throughput is limited by
> > many many factors
> > even without dummynet (or just because you have
> > traffic going through
> > other pipes, etc.).
> > 
> > finally, i don't know how wget computes times so it
> > may
> > be correct or not, i have no idea. since many
> > programs
> > do wrong things in computing bandwidths i wouldn't
> > give for granted that wget is correct in all
> > situations.
> > 
> > bye
> > luigi
> > 
> > 
> > > 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
> > > 
> 
> Let me ask my question differently then, do you think
> it is possible to bypass the pipe restriction (i.e.
> burst) for say the first 100KBytes ?

yes if you put a sufficiently large number in the line
to patch (ideally a configurable parameter).
of course you'll never go faster than your connection
allows without dummynet, and furthermore, 100k are way
beyond the amount of buffering that the socket or
ipintrq give you by default. you are likely to be slowed
down by any of these things.

i think i have said all i could on the subject

cheers
luigi
> 
> 
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