Add max_latency option

If set, fio will exit if it sees a total IO latency that exceeds
this value.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/HOWTO b/HOWTO
index 8eda99d..a7bd1fb 100644
--- a/HOWTO
+++ b/HOWTO
@@ -780,6 +780,9 @@
 		the job to exit. The same format as rate is used for read vs
 		write seperation.
 
+max_latency=int	If set, fio will exit the job if it exceeds this maximum
+		latency. It will exit with an ETIME error.
+
 ratecycle=int	Average bandwidth for 'rate' and 'ratemin' over this number
 		of milliseconds.