lib/pvector: Non-intrusive RCU priority vector.

Factor out the priority vector code from the classifier.

Making the classifier use RCU instead of locking requires parallel
access to the priority vector, pointing to subtables in descending
priority order.  When a new subtable is added, a new copy of the
priority vector is allocated, while the current readers can keep on
using the old copy they started with.  Adding and removing subtables
is usually less frequent than adding and removing rules, so this
should not have a visible performance implication.  As an optimization
for the userspace datapath use, where all the subtables have the same
priority, new subtables can be added to the end of the vector without
reallocation and without disturbing readers.

cls_subtables_reset() is now removed, as it served its purpose in bug
hunting.  Checks on the new pvector are now incorporated into
tests/test-classifier.c.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
lib/classifier: Optimize megaflows for single rule case.

When, during a classifier lookup, we narrow down to a single potential
rule, it is enough to match on ("unwildcard") one bit that differs
between the packet and the rule.

This is a special case of the more general algorithm, where it is
sufficient to match on enough bits that separates the packet from all
higher priority rules than the matched rule.  For a miss that would be
all the rules.  Implementing this is expensive for a more than a few
rules.  This patch starts by doing this for a single rule when we
already have it, also reducing the lookup cost by finishing the lookup
earlier than before.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
lib/classifier: Add miniflow_and_mask_matches_flow_wc.

miniflow_and_mask_matches_flow_wc() fills in the masks in flow
wildcards, so a separate step to that effect is no longer needed.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
lib/classifier: Clarify find_match_wc().

Reduce the number of goto statements by returning via a new helper
fill_range_wc() when no match is found.

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