fio: provide an option for a startdelay range
This patch allows the specification of start delay as range. With a
range each thread will chose an individual startdelay out of the range.
That solves an issue of startdelay being the same for each numjob clone
and that way spreads all kind of activities e.g. that all clones with
mixed r/w jobs switch r/w at the same time. Also all kind of other
"thundering herd" issues can be softened by some time spread due to this
option.
Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/fio.1 b/fio.1
index a16d039..2320ba3 100644
--- a/fio.1
+++ b/fio.1
@@ -846,8 +846,12 @@
allowed. For \fBbind\fR and \fBinterleave\fR, \fBnodelist\fR allows
comma delimited list of numbers, A-B ranges, or 'all'.
.TP
-.BI startdelay \fR=\fPint
-Delay start of job for the specified number of seconds.
+.BI startdelay \fR=\fPirange
+Delay start of job for the specified number of seconds. Supports all time
+suffixes to allow specification of hours, minutes, seconds and
+milliseconds - seconds are the default if a unit is ommited.
+Can be given as a range which causes each thread to choose randomly out of the
+range.
.TP
.BI runtime \fR=\fPint
Terminate processing after the specified number of seconds.