Re: [Patch] fix packet loss and massive ping spikes with PPP multi-link

[Ben McKeegan]

Ben McKeegan wrote:
> Paul Mackerras wrote:
>
> > > I needed to do something similar a while back and I took a very
> > > different approach, which I think is more flexible.   Rather than
> > > implement a new round-robin scheduler I simply introduced a target
> > > minimum fragment size into the fragment size calculation, as a per
> > > bundle parameter that can be configured via a new ioctl.  This
> > > modifies the algorithm so that it tries to limit the number of
> > > fragments such that each fragment is at least the minimum size.  If
> > > the minimum size is greater than the packet size it will not be
> > > fragmented all but will instead just get sent down the next
> > > available channel.
> > >
> > > A pppd plugin generates the ioctl call allowing this to be tweaked
> > > per connection.  It is more flexible in that you can still have the
> > > larger packets fragmented if you wish.
> >
> > I like this a lot better than the other proposed patch.  It adds less
> > code because it uses the fact that ppp_mp_explode() already has a
> > round-robin capability using the ppp->nxchan field, plus it provides a
> > way to control it per bundle via pppd.
> >
> > If you fix up the indentation issues (2-space indent in some of the
> > added code -- if you're using emacs, set c-basic-offset to 8), I'll
> > ack it and hopefully DaveM will pick it up.
>
> Okay, I'll fix it up when I'm back at work Tuesday and submit (today is 
> a UK public holiday) and also dig out and fix up the userspace code to 
> go with it.

Still working on this, updating the patch wasn't as trivial as I thought 
as it clashed with Gabriele Paoloni's ppp_mp_explode redesign.  However, 
while looking at this code I believe I have found a bug which might have 
been contributing to the poor performance the OP was experiencing.   For 
the case where channel speeds are unknown and there are more than 2 
channels it would miscalculate the fragment sizes so they are not 
balanced on the channels.

Patch for the bug to follow immediately.

Regards,
Ben.
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