add documentation about filename_format directory behavior

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 342bad803ac56adc062a153a74543a5d77f85f7c..a1513e1259f7cc3001fb185a662150a9527dba34 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -217,6 +217,9 @@ Command line options
 .. option:: --max-jobs=nr
 
        Set the maximum number of threads/processes to support to `nr`.
+       NOTE: On Linux, it may be necessary to increase the shared-memory
+       limit ('/proc/sys/kernel/shmmax') if fio runs into errors while
+       creating jobs.
 
 .. option:: --server=args
 
@@ -792,6 +795,13 @@ Target file/device
        named :file:`testfiles.4`. The default of :file:`$jobname.$jobnum.$filenum`
        will be used if no other format specifier is given.
 
+       If you specify a path then the directories will be created up to the
+       main directory for the file.  So for example if you specify
+       ``filename_format=a/b/c/$jobnum`` then the directories a/b/c will be
+       created before the file setup part of the job.  If you specify
+       :option:`directory` then the path will be relative that directory,
+       otherwise it is treated as the absolute path.
+
 .. option:: unique_filename=bool
 
        To avoid collisions between networked clients, fio defaults to prefixing any
@@ -1797,6 +1807,10 @@ I/O engine
                        absolute or relative. See :file:`engines/skeleton_external.c` for
                        details of writing an external I/O engine.
 
+               **filecreate**
+                       Simply create the files and do no IO to them.  You still need to
+                       set  `filesize` so that all the accounting still occurs, but no
+                       actual IO will be done other than creating the file.
 
 I/O engine specific parameters
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -2862,7 +2876,15 @@ 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