specify a number of IO's to do before getting a new offset, this is one by
appending a `:\fI<nr>\fR to the end of the string given. For a random read, it
would look like \fBrw=randread:8\fR for passing in an offset modifier with a
-value of 8. See the \fBrw_sequencer\fR option.
+value of 8. If the postfix is used with a sequential IO pattern, then the value
+specified will be added to the generated offset for each IO. For instance,
+using \fBrw=write:4k\fR will skip 4k for every write. It turns sequential IO
+into sequential IO with holes. See the \fBrw_sequencer\fR option.
.RE
.TP
.BI rw_sequencer \fR=\fPstr
coalescing adjacents IOs into a single submission.
.TP
.B libaio
-Linux native asynchronous I/O.
+Linux native asynchronous I/O. This engine also has a sub-option,
+\fBuserspace_reap\fR. To set it, use \fBioengine=libaio:userspace_reap\fR.
+Normally, with the libaio engine in use, fio will use the
+\fIio_getevents\fR\|(3) system call to reap newly returned events. With this
+flag turned on, the AIO ring will be read directly from user-space to reap
+events. The reaping mode is only enabled when polling for a minimum of \fB0\fR
+events (eg when \fBiodepth_batch_complete=0\fR).
.TP
.B posixaio
POSIX asynchronous I/O using \fIaio_read\fR\|(3) and \fIaio_write\fR\|(3).