stats: Add a function to report completion latency percentiles

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index b47d7335e30cb68f90ea2881803503755770d290..3b60f58e0e367d1e593de9337b78b0ffb47f5d24 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -244,6 +244,7 @@ irange      Integer range with suffix. Allows value range to be given, such
        1k:4k. If the option allows two sets of ranges, they can be
        specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see
        int.
        1k:4k. If the option allows two sets of ranges, they can be
        specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see
        int.

+float_list     A list of floating numbers, separated by a ':' character.

 
 With the above in mind, here follows the complete list of fio job
 parameters.
 
 With the above in mind, here follows the complete list of fio job
 parameters.


@@ -1120,6 +1121,18 @@ disable_slat=bool Disable measurements of submission latency numbers. See
 disable_bw=bool        Disable measurements of throughput/bandwidth numbers. See
                disable_lat.
 
 disable_bw=bool        Disable measurements of throughput/bandwidth numbers. See
                disable_lat.
 

+clat_percentiles=bool Enable the reporting of percentiles of
+                completion latencies.
+
+percentile_list=float_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, and
+               list the numbers in ascending order. 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.
+

 gtod_reduce=bool Enable all of the gettimeofday() reducing options
                (disable_clat, disable_slat, disable_bw) plus reduce
                precision of the timeout somewhat to really shrink
 gtod_reduce=bool Enable all of the gettimeofday() reducing options
                (disable_clat, disable_slat, disable_bw) plus reduce
                precision of the timeout somewhat to really shrink