Re: Route cache performance under stress

[Ralph Doncaster <ralph@xxxxxxxxx>]

On Tue, 10 Jun 2003, David S. Miller wrote:

> 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 :)

Looking at Simon's profile numbers, these seem to contribute a lot more
than fib_validate_source:
  1237 ipt_route_hook                            19.3281
  3120 do_gettimeofday                           21.6667
  8299 ip_packet_match                           24.6994
  8031 fib_lookup                                25.0969
  1877 fib_rule_put                              29.3281

What's the do_gettimeofday for?  Is that just a bogus one that shows up
for kernel profiling (I can recall using the profiling tool quantify had a
similar problem of showing gettimeofday calls that it was doing on its
own).

I traced back the fib_lookup to ip_forward_finish, which seems to only
call ip_forward_options when there's IP options (go figure!), which would
make sense for a SYN packet (juno).  What I can't think of is why we'd
want to have special routing considerations for TCP SYN packets (and other
IP packets with options set).

-Ralph