UMA supports "secondary" zones, in which a second zone can be layered
on top of a primary zone, sharing the same allocation "keg". When
reporting statistics for zones, do not report the free items i

UMA supports "secondary" zones, in which a second zone can be layered
on top of a primary zone, sharing the same allocation "keg". When
reporting statistics for zones, do not report the free items in the
keg as part of the free items in the zone, or those free items will
be reported more than once: for the primary zone, and then any
secondary zones off the primary zone. Separately record and maintain
a kegfree statistic, and export via memstat_get_kegfree(), which is
available for use if needed. Since items free'd back to the keg are
not fully initialized, and hence may not actually be available (since
secondary zone ctor-time initialization can fail), this makes some
amount of sense.

This change corrects a bug made visible in the libmemstat(3)
modifications to netstat: mbufs freed back to the keg from the
packet zone would be counted twice, resulting in negative values
being printed in the mbuf free count.

Some further refinement of reporting relating to secondary zones may
still be required.

Reported by: ssouhlal
MFC after: 3 days

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Increase the number of caller memory storage slots from 2 or 4 to
MEMSTAT_MAXCALLER (8), and expose MEMSTAT_MAXCALLER via memstat.h so
that applications can check their assumptions about how many slo

Increase the number of caller memory storage slots from 2 or 4 to
MEMSTAT_MAXCALLER (8), and expose MEMSTAT_MAXCALLER via memstat.h so
that applications can check their assumptions about how many slots
are available.

Remove 'spare' memory storage in struct malloc_type, since we now
don't expose the data structure internals to applications and rely
on accessor methods, this approach to ABI stability isn't required.

MFC after: 7 days

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Add libmemstat(3), a library for use by debugging and monitoring
applications in tracking kernel memory statistics. It provides an
abstracted interface to uma(9) and malloc(9) statistics, wrapped
ar

Add libmemstat(3), a library for use by debugging and monitoring
applications in tracking kernel memory statistics. It provides an
abstracted interface to uma(9) and malloc(9) statistics, wrapped
around the recently added binary stream sysctls for the allocators.

Using this interface, it is easy to build monitoring tools, query
specific memory types for usage information, etc. Facilities are
provided for binding caller-provided data to memory types,
incremental updates of memory types, and queries that span multiple
allocators.

Support for additional allocators is (relatively) easy to add.

The API for libmemstat(3) will probably change some over time as
consumers are written, and requirements evolve. It is written to
avoid encoding ABIs for data structure layout into consuming
applications for this reason.

MFC after: 1 week

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