lib: objagg: add root count to stats

Count number of roots and add it to stats. It is handy for the library
user to have this stats available as it can act upon it without
counting roots itself.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

lib: objagg: implement optimization hints assembly and use hints for object creation

Implement simple greedy algo to find more optimized root-delta tree for
a given objagg instance. This "hints" can be used by a driver to:
1) check if the hints are better (driver's choice) than the original
objagg tree. Driver does comparison of objagg stats and hints stats.
2) use the hints to create a new objagg instance which will construct
the root-delta tree according to the passed hints. Currently, only a
simple greedy algorithm is implemented. Basically it finds the roots
according to the maximal possible user count including deltas.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

lib: introduce initial implementation of object aggregation manager

This lib tracks objects which could be of two types:
1) root object
2) nested object - with a "delta" which differentiates it from
the associated root object
The objects are tracked by a hashtable and reference-counted. User is
responsible of implementing callbacks to create/destroy root entity
related to each root object and callback to create/destroy nested object
delta.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>