stats: Add a function to report completion latency percentiles

    This patch introduces two new options:
    1) Specifying --clat_percentiles enables the reporting of
       completion latency percentiles.
    2) --percentile_list allows the user to customize the
       list of percentiles to report.

    Signed-off-by: Yu-ju Hong <yjhong@google.com>

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/fio.1 b/fio.1
index 4fcd511..40940f3 100644
--- a/fio.1
+++ b/fio.1
@@ -96,6 +96,10 @@
 \fIupper\fR may contain a suffix as described above.  If an option allows two
 sets of ranges, they are separated with a `,' or `/' character. For example:
 `8\-8k/8M\-4G'.
+.TP
+.I float_list
+List of floating numbers: A list of floating numbers, separated by
+a ':' charcater.
 .SS "Parameter List"
 .TP
 .BI name \fR=\fPstr
@@ -900,6 +904,17 @@
 .TP
 .BI gid \fR=\fPint
 Set group ID, see \fBuid\fR.
+.TP
+.BI clat_percentiles \fR=\fPbool
+Enable the reporting of percentiles of completion latencies.
+.TP
+.BI percentile_list \fR=\fPfloat_list
+Overwrite the default list of percentiles for completion
+latencies. Each number is a floating number in the range (0,100], and
+the maximum length of the list is 20. Use ':' to separate the
+numbers. For example, --percentile_list=99.5:99.9 will cause fio to
+report the values of completion latency below which 99.5% and 99.9% of
+the observed latencies fell, respectively.
 .SH OUTPUT
 While running, \fBfio\fR will display the status of the created jobs.  For
 example: