[Babel-users] Ability to work with massive number of routes? (global full-table)

[Juliusz Chroboczek]

> Well, I took a stab at some of that. In particular, babeld has to compare
> a lot of bytes, and while profiling it on these loads, was totally
> bottlenecked on memcmp.

Yep, the code in xroute.c is pretty pessimal, since I wan't expecting
people to have massive numbers of redistributed routes.  That's easily
fixed, though.

Note that this does not apply to normal routes (learned from other Babel
speakers) -- if your profiling shows any hotspots in route.c, then I'm
interested.

> And - setting a goal for 64k routes - I thought that switching to
> a normalized table structure internally would be useful. Instead of
> storing the nexthop as a full address store an 16 bit index pointing to
> an array of those nexthops.

We already do (except that we use a pointer rather than an integer index),
see struct route in route.h.

> We could write a roadmap for "better wifi mesh networking", but it
> starts with "more bodies".

Hehe.

> * walking linked lists

Hm.  If you're seeing that in your profiles, then your network is very
dense -- only redundant (unused) routes are kept in linked lists.  May
I see your profile, please?

> * running out of bandwidth

I think it's the bursty nature of the traffic that kills you, not the
average throughput.  I'll definitely be working on that, but I first need
to reproduce your results in a controlled situation.

> * recalcing bellman-ford

That shouldn't cost much, since the computation is incremental.  If it
does, I need to see your profile.

-- Juliusz