Add options to have fio latency profile a device
This adds three new options:
- latency_target. This defines a specific latency target, in usec.
- latency_window. This defines the period over which fio samples.
- latency_percentile. This defines the percentage of IOs that must
meet the criteria specified by latency_target/latency_window.
With these options set, fio will run the described workload and
vary the queue depth between 1 and iodepth= to find the best
performing spot that meets the criteria specified by the three
options.
A sample job file is also added to demonstrate how to use this.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fio.1 b/fio.1
index 15a1ac5..9ee0eef 100644
--- a/fio.1
+++ b/fio.1
@@ -764,6 +764,23 @@
Average bandwidth for \fBrate\fR and \fBratemin\fR over this number of
milliseconds. Default: 1000ms.
.TP
+.BI latency_target \fR=\fPint
+If set, fio will attempt to find the max performance point that the given
+workload will run at while maintaining a latency below this target. The
+values is given in microseconds. See \fBlatency_window\fR and
+\fBlatency_percentile\fR.
+.TP
+.BI latency_window \fR=\fPint
+Used with \fBlatency_target\fR to specify the sample window that the job
+is run at varying queue depths to test the performance. The value is given
+in microseconds.
+.TP
+.BI latency_percentile \fR=\fPfloat
+The percentage of IOs that must fall within the criteria specified by
+\fBlatency_target\fR and \fBlatency_window\fR. If not set, this defaults
+to 100.0, meaning that all IOs must be equal or below to the value set
+by \fBlatency_target\fR.
+.TP
.BI max_latency \fR=\fPint
If set, fio will exit the job if it exceeds this maximum latency. It will exit
with an ETIME error.