Add iodepth_batch_complete control
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/HOWTO b/HOWTO
index 12974f3..50ca467 100644
--- a/HOWTO
+++ b/HOWTO
@@ -433,11 +433,21 @@
job, can be overridden with a larger value for higher
concurrency.
+iodepth_batch_submit=int
iodepth_batch=int This defines how many pieces of IO to submit at once.
It defaults to 1 which means that we submit each IO
as soon as it is available, but can be raised to submit
bigger batches of IO at the time.
+iodepth_batch_complete=int This defines how many pieces of IO to retrieve
+ at once. It defaults to 1 which means that we'll ask
+ for a minimum of 1 IO in the retrieval process from
+ the kernel. The IO retrieval will go on until we
+ hit the limit set by iodepth_low. If this variable is
+ set to 0, then fio will always check for completed
+ events before queuing more IO. This helps reduce
+ IO latency, at the cost of more retrieval system calls.
+
iodepth_low=int The low water mark indicating when to start filling
the queue again. Defaults to the same as iodepth, meaning
that fio will attempt to keep the queue full at all times.