test-classifier: Add benchmark.

test-classifier: Add benchmark.

Add a benchmark command for classifier lookup performance testing.

Running the test-classifier without arguments of with "--help" will
print the following usage:

usage: ovstest test-classifier benchmark <n_rules> <n_priorities> <n_subtables> <n_threads> <n_lookups>

where:

<n_rules>      - The number of rules to install for lookups.  More rules
                 makes misses less likely.
<n_priorities> - How many different priorities to use.  Using only 1
                 priority will force lookups to continue through all
                 subtables.
<n_subtables>  - Number of subtables to use.  Normally a classifier has
                 rules with different kinds of masks, resulting in
                 multiple subtables (one per mask).  However, in some
                 special cases a table may consist of only one kind of
                 rules, so there will be only one subtable.
<n_threads>    - How many lookup threads to use.  Using one thread should
                 give less variance accross runs, but classifier
                 scaling can be tested with multiple threads.
<n_lookups>    - How many lookups each thread should perform.

For testing the classifier is filled with <n_rules> rules using
<n_subtables> different mask patterns and <n_priorities> different
priorities.  A random set of lookup flows are created, and <n_threads>
lookup threads are spawned to perform <n_lookups> lookups each.  The
count of hits and misses, as well as the overall execution time is
reported.

Example run:

$ tests/ovstest test-classifier benchmark 1000 1 30 1 3800000

Benchmarking with:
1000 rules with 1 priorities in 30 tables, 1 threads doing 3800000 lookups each

Without wildcards:

hits: 461520, misses: 3338480
classifier lookups:    386 ms, 9844559 lookups/sec

With wildcards:

hits: 461520, misses: 3338480
classifier lookups:    866 ms, 4387990 lookups/sec

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>