Documentation: dm-integrity: Document an example of how the tunables relate.

Signed-off-by: Russell Harmon <eatnumber1@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Documentation/admin-guide/device-mapper/dm-integrity.rst

@@ -213,6 +213,12 @@ table and swap the tables with suspend and resume). The other arguments
 should not be changed when reloading the target because the layout of disk
 data depend on them and the reloaded target would be non-functional.
 
+For example, on a device using the default interleave_sectors of 32768, a
+block_size of 512, and an internal_hash of crc32c with a tag size of 4
+bytes, it will take 128 KiB of tags to track a full data area, requiring
+256 sectors of metadata per data area. With the default buffer_sectors of
+128, that means there will be 2 buffers per metadata area, or 2 buffers
+per 16 MiB of data.
 
 Status line: