What:  /sys/kernel/mm/cma/
Date:  Feb 2021
Contact: Minchan Kim <minchan@kernel.org>
Description:
  /sys/kernel/mm/cma/ contains a subdirectory for each CMA
  heap name (also sometimes called CMA areas).

  Each CMA heap subdirectory (that is, each
  /sys/kernel/mm/cma/<cma-heap-name> directory) contains the
  following items:

   alloc_pages_success
   alloc_pages_fail

What:  /sys/kernel/mm/cma/<cma-heap-name>/alloc_pages_success
Date:  Feb 2021
Contact: Minchan Kim <minchan@kernel.org>
Description:
  the number of pages CMA API succeeded to allocate

What:  /sys/kernel/mm/cma/<cma-heap-name>/alloc_pages_fail
Date:  Feb 2021
Contact: Minchan Kim <minchan@kernel.org>
Description:
  the number of pages CMA API failed to allocate

What:  /sys/kernel/mm/cma/<cma-heap-name>/release_pages_success
Date:  Feb 2024
Contact: Anshuman Khandual <anshuman.khandual@arm.com>
Description:
  the number of pages CMA API succeeded to release

What:  /sys/kernel/mm/cma/<cma-heap-name>/total_pages
Date:  Jun 2024
Contact: Frank van der Linden <fvdl@google.com>
Description:
  The size of the CMA area in pages.

What:  /sys/kernel/mm/cma/<cma-heap-name>/available_pages
Date:  Jun 2024
Contact: Frank van der Linden <fvdl@google.com>
Description:
  The number of pages in the CMA area that are still
  available for CMA allocation.