From: Jamal Hadi <hadi@xxxxxxxxxxxxxxxx>
Date: Sun, 8 Jun 2003 23:15:46 -0400 (EDT)
The more i think about it the more i think CEF is a lame escape
from route caches.
It is one perspective :-)
What we need is multi-tries at the slow path and
perhaps a binary tree on hash collisions buckets of the dst cache
(instead of a linked list).
I do not believe that slow path is slow. In fact after I fixed
hash table growth in fib_hash.c Simon showed us clearly how DoS
performance was _NOT_ tied to the number of routes loaded into
What is slow are things like fib_validate_source() on SMP and the GC
(and some other things, I need to study Simon's profiles more deeply).
The GC is aparently really badly behaved now during DoS like traffic.
My main current quick idea is to make rt_intern_hash() attempt
to flush out entries in the same hash chain instead of allocating
I also question the setting of ip_rt_max_size in relation to the
number of hash chains (it's set to n_hashchains * 16 currently,
that sounds wrong, maybe something more like n_hashchains * 2 or
even n_hashchains * 3).
I'll try to cook up a patch to test. We might even be able to
kill of route cache GC entriely if this scheme works well.