Add support for idletime profiling

Idletime profiling allows a benchmark to run while filling the
idle cycles on the server, hence giving you some metric of how
much pressure the system is under. This is useful to be able
to profile and compare changes in a setup or driver, for instance.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fio.1 b/fio.1
index 1f81ea7..6b7e945 100644
--- a/fio.1
+++ b/fio.1
@@ -77,6 +77,9 @@
 .TP
 .BI \-\-client \fR=\fPhost
 Instead of running the jobs locally, send and run them on the given host.
+.TP
+.BI \-\-idle\-prof \fR=\fPoption
+Report cpu idleness on a system or percpu basis (\fIoption\fP=system,percpu) or run unit work calibration only (\fIoption\fP=calibrate).
 .SH "JOB FILE FORMAT"
 Job files are in `ini' format. They consist of one or more
 job definitions, which begin with a job name in square brackets and