Improve on the ZFS events documentation

* Add information about the 'zpool events' command in zpool(8).
* More events and payloads defined in zfs-events(5).
* I/O Stages and I/O Flags sections added.
* Remove unused legacy "zio_deadline" payload define.

Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3467

man/man8/zpool.8

@@ -55,6 +55,11 @@ zpool \- configures ZFS storage pools
 \fBzpool detach\fR \fIpool\fR \fIdevice\fR
 .fi
 
+.LP
+.nf
+\fBzpool events\fR [\fB-vHfc\fR] [\fIpool\fR] ...
+.fi
+
 .LP
 .nf
 \fBzpool export\fR [\fB-a\fR] [\fB-f\fR] \fIpool\fR ...
@@ -1061,6 +1066,62 @@ Detaches \fIdevice\fR from a mirror. The operation is refused if there are no ot
 
 .RE
 
+.sp
+.ne 2
+.mk
+.na
+\fBzpool events\fR [\fB-vHfc\fR] [\fIpool\fR] ...
+.ad
+.sp .6
+.RS 4n
+Description of the different events generated by the ZFS kernel modules. See \fBzfs-events\fR(5) for more information about the subclasses and event payloads that can be generated.
+
+.sp
+.ne 2
+.mk
+.na
+\fB\fB-v\fR\fR
+.ad
+.RS 6n
+.rt
+Get a full detail of the events and what information is available about it.
+.RE
+
+.sp
+.ne 2
+.mk
+.na
+\fB\fB-H\fR\fR
+.ad
+.RS 6n
+.rt
+Scripted mode. Do not display headers, and separate fields by a single tab instead of arbitrary space.
+.RE
+
+.sp
+.ne 2
+.mk
+.na
+\fB\fB-f\fR\fR
+.ad
+.RS 6n
+.rt
+Follow mode.
+.RE
+
+.sp
+.ne 2
+.mk
+.na
+\fB\fB-c\fR\fR
+.ad
+.RS 6n
+.rt
+Clear all previous events.
+.RE
+
+.RE
+
 .sp
 .ne 2
 .mk
@@ -2333,4 +2394,4 @@ Similar to the \fB-d\fR option in \fIzpool import\fR.
 .SH SEE ALSO
 .sp
 .LP
-\fBzfs\fR(8), \fBzpool-features\fR(5)
+\fBzfs\fR(8), \fBzpool-features\fR(5), \fBzfs-events\fR(5)