+4.2 Reserved keywords
+---------------------
+
+Additionally, fio has a set of reserved keywords that will be replaced
+internally with the appropriate value. Those keywords are:
+
+$pagesize The architecture page size of the running system
+$mb_memory Megabytes of total memory in the system
+$ncpus Number of online available CPUs
+
+These can be used on the command line or in the job file, and will be
+automatically substituted with the current system values when the job
+is run. Simple math is also supported on these keywords, so you can
+perform actions like:
+
+size=8*$mb_memory
+
+and get that properly expanded to 8 times the size of memory in the
+machine.
+