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Message-Id: <200905091735.15235.czoccolo@gmail.com>
Date: Sat, 9 May 2009 17:35:14 +0200
From: Corrado Zoccolo <czoccolo@...il.com>
To: "Jens Axboe" <jens.axboe@...cle.com>
Cc: "Linux-Kernel" <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/2] deadline-iosched: code cleanup, preparation for sync/async patch
This is the first patch of the series, and contains code cleanup
needed before changing read/write to sync/async.
No behavioral change is introduced by this patch.
Code cleanups:
* A single next_rq is sufficient.
* we store fifo insertion time on request, and compute deadline on the
fly, to handle fifo_expire changes better (fifos remain sorted)
* remove unused field
* deadline_latter_request becomes deadline_next_request.
Signed-off-by: Corrado Zoccolo <czoccolo@...il.com>
---
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index c4d991d..5713595 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -35,11 +35,10 @@ struct deadline_data {
struct list_head fifo_list[2];
/*
- * next in sort order. read, write or both are NULL
+ * next in sort order.
*/
- struct request *next_rq[2];
+ struct request *next_rq;
unsigned int batching; /* number of sequential requests made */
- sector_t last_sector; /* head position */
unsigned int starved; /* times reads have starved writes */
/*
@@ -63,7 +62,7 @@ deadline_rb_root(struct deadline_data *dd, struct request *rq)
* get the request after `rq' in sector-sorted order
*/
static inline struct request *
-deadline_latter_request(struct request *rq)
+deadline_next_request(struct request *rq)
{
struct rb_node *node = rb_next(&rq->rb_node);
@@ -86,10 +85,8 @@ deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
static inline void
deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
{
- const int data_dir = rq_data_dir(rq);
-
- if (dd->next_rq[data_dir] == rq)
- dd->next_rq[data_dir] = deadline_latter_request(rq);
+ if (dd->next_rq == rq)
+ dd->next_rq = deadline_next_request(rq);
elv_rb_del(deadline_rb_root(dd, rq), rq);
}
@@ -101,15 +98,14 @@ static void
deadline_add_request(struct request_queue *q, struct request *rq)
{
struct deadline_data *dd = q->elevator->elevator_data;
- const int data_dir = rq_data_dir(rq);
deadline_add_rq_rb(dd, rq);
/*
- * set expire time and add to fifo list
+ * set request creation time and add to fifo list
*/
- rq_set_fifo_time(rq, jiffies + dd->fifo_expire[data_dir]);
- list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
+ rq_set_fifo_time(rq, jiffies);
+ list_add_tail(&rq->queuelist, &dd->fifo_list[rq_data_dir(rq)]);
}
/*
@@ -206,13 +202,7 @@ deadline_move_to_dispatch(struct deadline_data *dd, struct request *rq)
static void
deadline_move_request(struct deadline_data *dd, struct request *rq)
{
- const int data_dir = rq_data_dir(rq);
-
- dd->next_rq[READ] = NULL;
- dd->next_rq[WRITE] = NULL;
- dd->next_rq[data_dir] = deadline_latter_request(rq);
-
- dd->last_sector = rq_end_sector(rq);
+ dd->next_rq = deadline_next_request(rq);
/*
* take it off the sort and fifo list, move
@@ -227,15 +217,13 @@ deadline_move_request(struct deadline_data *dd, struct request *rq)
*/
static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
{
- struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
-
+ BUG_ON(list_empty(&dd->fifo_list[ddir]));
/*
- * rq is expired!
+ * deadline is expired!
*/
- if (time_after(jiffies, rq_fifo_time(rq)))
- return 1;
-
- return 0;
+ return time_after(jiffies, dd->fifo_expire[ddir] +
+ rq_fifo_time(rq_entry_fifo(dd->fifo_list[ddir].next))
+ );
}
/*
@@ -247,20 +235,13 @@ static int deadline_dispatch_requests(struct request_queue *q, int force)
struct deadline_data *dd = q->elevator->elevator_data;
const int reads = !list_empty(&dd->fifo_list[READ]);
const int writes = !list_empty(&dd->fifo_list[WRITE]);
- struct request *rq;
+ struct request *rq = dd->next_rq;
int data_dir;
- /*
- * batches are currently reads XOR writes
- */
- if (dd->next_rq[WRITE])
- rq = dd->next_rq[WRITE];
- else
- rq = dd->next_rq[READ];
-
- if (rq && dd->batching < dd->fifo_batch)
+ if (rq && dd->batching < dd->fifo_batch) {
/* we have a next request are still entitled to batch */
goto dispatch_request;
+ }
/*
* at this point we are not running a batch. select the appropriate
@@ -299,7 +280,9 @@ dispatch_find_request:
/*
* we are not running a batch, find best request for selected data_dir
*/
- if (deadline_check_fifo(dd, data_dir) || !dd->next_rq[data_dir]) {
+ if (!dd->next_rq
+ || rq_data_dir(dd->next_rq) != data_dir
+ || deadline_check_fifo(dd, data_dir)) {
/*
* A deadline has expired, the last request was in the other
* direction, or we have run out of higher-sectored requests.
@@ -311,7 +294,7 @@ dispatch_find_request:
* The last req was the same dir and we have a next request in
* sort order. No expired requests so continue on from here.
*/
- rq = dd->next_rq[data_dir];
+ rq = dd->next_rq;
}
dd->batching = 0;
--
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