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Subject[PATCH 2/3] Deadline iosched: Reset batch for ordered requests
The deadline I/O scheduler does not reset the batch count when starting
a new batch at a higher-sectored request. This means the second and
subsequent batch in the same data direction will never exceed a single
request in size whenever higher-sectored requests are pending.

This patch gives new batches in the same data direction as old ones
their full quota of requests by resetting the batch count.

Signed-off-by: Aaron Carroll <aaronc@gelato.unsw.edu.au>
---
block/deadline-iosched.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index a44437e..cb94c83 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -306,12 +306,11 @@ dispatch_writes:
dispatch_find_request:
/*
* we are not running a batch, find best request for selected data_dir
+ * and start a new batch
*/
if (deadline_check_fifo(dd, data_dir)) {
/* An expired request exists - satisfy it */
- dd->batching = 0;
rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
-
} else if (dd->next_rq[data_dir]) {
/*
* The last req was the same dir and we have a next request in
@@ -325,12 +324,13 @@ dispatch_find_request:
* higher-sectored requests. Go back to the lowest sectored
* request (1 way elevator) and start a new batch.
*/
- dd->batching = 0;
node = rb_first(&dd->sort_list[data_dir]);
if (node)
rq = rb_entry_rq(node);
}

+ dd->batching = 0;
+
dispatch_request:
/*
* rq is the selected appropriate request.
-
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