shm Use shared memory as the buffers. Allocated
through shmget(2).
+ shmhuge Same as shm, but use huge pages as backing.
+
mmap Use anonymous memory maps as the buffers.
Allocated through mmap(2).
+ mmaphuge Use a memory mapped huge file as the buffer
+ backing. Append filename after mmaphuge, ala
+ mem=mmaphuge:/hugetlbfs/file
+
The area allocated is a function of the maximum allowed
bs size for the job, multiplied by the io depth given.