Per-CPU VFS Namecache Effectiveness Statistics:

Per-CPU VFS Namecache Effectiveness Statistics:

	* Convert nchstats into a CPU indexed array

	* Export the per-CPU nchstats as a sysctl vfs.cache.nchstats
	  and let user-land aggregate them.

	* Add a function called kvm_nch_cpuagg() to libkvm; it is
	  shared by systat(1) and vmstat(1) and the ncache-stats test
	  program.  As the function name suggests, it aggregates
	  the per-CPU nchstats.

	* Move struct nchstats into a separate header to avoid
	  header file namespace pollution; sys/nchstats.h.

	* Keep a cached copy of the globaldata pointer in the VFS
	  specific LOOKUP op, and use that to increment the
	  namecache effectiveness counters (nchstats).

	* Modify systat(1) and vmstat(1) to accomodate the new
	  behavior of accessing nchstats.  Remove a (now) redundant
	  sysctl to get the cpu count (hw.ncpu), instead we just divide
	  the total length of the nchstats array returned by sysctl
	  by sizeof(struct nchstats) to get the CPU count.

	* Garbage-collect unused variables and fix nearby warnings
	  in systat(1) an vmstat(1).

	* Add a very-cool test program, that prints the nchstats
	  per-CPU statistics to show CPU distribution.  Here is the
	  output it generates on an 2-processor SMP machine:

	  gray# ncache-stats
	  VFS Name Cache Effectiveness Statistics
  	  4207370 total name lookups
	  COUNTER             CPU-1       CPU-2           TOTAL
	  goodhits            2477657     1060677         (3538334  )
	  neghits             107531      47294           (154825   )
	  badhits             28968       7720            (36688    )
	  falsehits           0           0               (0        )
	  misses              339671      137852          (477523   )
	  longnames           0           0               (0        )
	  passes 2            13104       6813            (19917    )
	  2-passes            25134       15257           (40391    )

The SMP machine used for testing this commit was proudly presented
by David Rhodus <drhodus@dragonflybsd.org>.

Reviewed-by:	Matthew Dillon <dillon@backplane.com>