Re: Route cache performance under stress

[Robert Olsson <Robert.Olsson@xxxxxxxxxxx>]

David S. Miller writes:

 > How did you "rip it out"?  Just never look into the routing
 > cache hash and never add entries there?  If so, then yes it is
 > excellent simulation for pure slow path.

 Look at the patch... 
 hash lookup is bypassed -> always slow path. no lookup in rt_intern_hash
 but we keep the entry in the hash and ip_rt_dst_alloc is changed to run
 do __rt_hash_shrink for each call.

 > This is not purely an algorithmic problem.  The highest cost thing we
 > do in the slow path of input route processing is source validation.
 > This requires real brains to eliminate.
 > 
 > Actually, that's a good idea, if someone if brave just rip out
 > fib_validate_source (just don't call it, should work for valid
 > traffic) and see what happens :)

 It should be easy to do... 

 Cheers.
                                                --ro