- 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
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.
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
