16-CPU #s for lockfree rtcache (rt_rcu)

[Dipankar Sarma <dipankar@in.ibm.com>]

As promised, here is the kernprof data from the simulated
test suggested by Dave. The test uses 32 processes and dest
addresses for rtcache lookup are random, changing after every 5 packets.
The measurements were done in a 16 CPU NUMA-Q.

2.5.3 : ip_route_output_key [c01bab8c]: 12166
2.5.3+rt_rcu : ip_route_output_key [c01bb084]: 6027

I have seen moderately significant profile counts
for ip_route_input() in preliminary webserver benchmark runs.
It is not however clear to me that bucket lock cache line
bouncing is the reason behind it. That one needs more investigation.

Thanks
-- 
Dipankar Sarma  <dipankar@in.ibm.com> http://lse.sourceforge.net
Linux Technology Center, IBM Software Lab, Bangalore, India.