Add support for doing total latency percentiles

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 3a720c35b68e59d948921689ac56b6c2bfc7e95d..bfaa054a5de0e84e1d914d2b2375c041c00eb57b 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -1791,7 +1791,9 @@ I/O engine
                **external**
                        Prefix to specify loading an external I/O engine object file. Append
                        the engine filename, e.g. ``ioengine=external:/tmp/foo.o`` to load
-                       ioengine :file:`foo.o` in :file:`/tmp`.
+                       ioengine :file:`foo.o` in :file:`/tmp`. The path can be either
+                       absolute or relative. See :file:`engines/skeleton_external.c` for
+                       details of writing an external I/O engine.
 
 
 I/O engine specific parameters
@@ -2858,7 +2860,15 @@ Measurements and reporting
 
 .. option:: clat_percentiles=bool
 
-       Enable the reporting of percentiles of completion latencies.
+       Enable the reporting of percentiles of completion latencies.  This
+       option is mutually exclusive with :option:`lat_percentiles`.
+
+.. option:: lat_percentiles=bool
+
+       Enable the reporting of percentiles of IO latencies. This is similar
+       to :option:`clat_percentiles`, except that this includes the
+       submission latency. This option is mutually exclusive with
+       :option:`clat_percentiles`.
 
 .. option:: percentile_list=float_list