Change history of the perfstat API

The following changes and additions have been made to the perfstat APIs.

Interface changes
With the following filesets the rblks and wblks fields of libperfstat are represented by blocks of 512 bytes in the perfstat_disk_total_t, perfstat_diskadapter_t and perfstat_diskpath_t structures, regardless of the actual block size used by the device for which metrics are being retrieved.
Interface additions
Review the specific interfaces that are available for a fileset.
Field additions
The following additions have been made to the specified file set levels.
Structure additions
Review the specific structure additions that are available for different file sets.

Parent topic: Perfstat API programming