Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Get rid of MAXCPU knowledge used for internal needs only. Switch to
dynamic memory allocation to hold per-CPU memory types data (sized to
mp_maxid for UMA, and to mp_maxcpus for malloc to match the kernel).

That fixes libmemstat with arbitrary large MAXCPU values and therefore
eliminates MEMSTAT_ERROR_TOOMANYCPUS error type.

Reviewed by: jhb
Approved by: re (kib)

Update the KVM backend for malloc stats to catch up to the internal structure
BI change from the addition of DTrace malloc(9) probes.

Submitted by: Ben Kelly ben of wanderview dot com

Make pointer argument to kread_string() const since the kernel structure
field is const, and then employ __DECONST before getting into the kvm
code. This eliminates a gcc 4.2 warning about losing constification.

__DECONST advice from: sam

Teach libmemstat(3) how to extract malloc(9) statistics using kvm(3),
so that libmemstat can be used to view full memory statistics from
kernel core dumps and /dev/mem. This is provided via a new query
function, memstat_kvm_malloc(), which is also automatically invoked
by memstat_kvm_all(). A kvm handle must be passed in.

This will allow malloc(9)-specific code to be removed from vmstat(8).

Correct two libmemstat(3) bugs:

- Move memory_type_list flushing logic from memstat_mtl_free() to
_memstat_mtl_empty(), a libmemstat-internal function that can
be called from other parts of the library. Invoke
_memstat_mtl_empty() from memstat_mtl_free(), which also frees
the containing list structure.

Invoke _memstat_mtl_empty() instead of memstat_mtl_free() in
various error cases in memstat_malloc.c and memstat_uma.c, which
previously resulted in the list being freed prematurely.

- Reverse the order of updating the mt_kegfree and mt_free fields
of the memory_type in memstat_uma.c, otherwise keg free items
won't be counted properly for non-secondary zones.

MFC after: 3 days

Introduce more formal error handling for libmemstat(3):

- Define a set of libmemstat(3) error constants, which are used by all
libmemstat(3) methods except for memstat_mtl_alloc(), which allocates
a memory type list and may return ENOMEM via errno.

- Define a per-memory_type_list current error value, which is set when a
call associated with a memory list fails. This requires wrapping a
structure around the queue(9) list head data structure, but this change
is not visible to libmemstat(3) consumers due to using access methods.

- Add a new accessor method, memstat_mtl_geterror() to retrieve the error
number.

- Consistently set the error number in a number of failure modes where
previously some combination of setting errno and printf'ing error
descriptions was used. libmemstat(3) will now no longer print to stdio
under any circumstances. Returns of NULL/-1 for errors remain the
same.

This avoids use of stdio, misuse of error numbers, and should make it
easier to program a libmemstat(3) consumer able to print useful error
messages. Currently, no error-to-string function is provided, as I'm
unsure how to address internationalization concerns.

MFC after: 1 day

Prefix two non-static libmemstat(3) internal functions with '_' symbols, to
try and discourage use outside the library.

Remove duplicate declaration of memstat_mtl_free() from memstat_internal.h,
as it's not internal, and the memstat.h definition suffices.

Re-spell wronge less wrongly as wrong.

Submitted by: jkoshy
MFC after: 1 week

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