block/deadline-iosched.c | 120 ++++++++++++++++++++++++-----------------------
1 files changed, 63 insertions(+), 57 deletions(-)
diff -puN drivers/block/deadline-iosched.c~deadline-np-42 drivers/block/deadline-iosched.c
--- 25/drivers/block/deadline-iosched.c~deadline-np-42 2003-01-28 21:35:14.000000000 -0800
+++ 25-akpm/drivers/block/deadline-iosched.c 2003-01-28 21:35:14.000000000 -0800
@@ -53,15 +53,13 @@ struct deadline_data {
struct rb_root sort_list[2];
struct list_head fifo_list[2];
- /*
- * next in sort order. read, write or both are NULL
- */
- struct deadline_rq *next_drq[2];
+ struct deadline_rq *next_drq[2];/* next in sort order */
+ sector_t last_sector[2]; /* last READ and WRITE sectors */
struct list_head *dispatch; /* driver dispatch queue */
struct list_head *hash; /* request hash */
unsigned long hash_valid_count; /* barrier hash count */
unsigned int batching; /* number of sequential requests made */
- sector_t last_sector; /* head position */
+ int batch_data_dir; /* current/last batch READ or WRITE */
unsigned int starved; /* times reads have starved writes */
/*
@@ -166,6 +164,27 @@ deadline_find_drq_hash(struct deadline_d
#define DRQ_RB_ROOT(dd, drq) (&(dd)->sort_list[rq_data_dir((drq)->request)])
#define rq_rb_key(rq) (rq)->sector
+/*
+ * deadline_find_first_drq finds the first (lowest sector numbered) request
+ * for the specified data_dir. Used to sweep back to the start of the disk
+ * (1-way elevator) after we process the last (highest sector) request.
+ */
+static struct deadline_rq *
+deadline_find_first_drq(struct deadline_data *dd, int data_dir)
+{
+ struct rb_node *n = dd->sort_list[data_dir].rb_node;
+
+ if (n == NULL)
+ return NULL;
+
+ for (;;) {
+ if (n->rb_left == NULL)
+ return rb_entry_drq(n);
+
+ n = n->rb_left;
+ }
+}
+
static struct deadline_rq *
__deadline_add_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
{
@@ -193,7 +212,29 @@ static int
deadline_add_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
{
struct deadline_rq *__alias;
+ const int data_dir = rq_data_dir(drq->request);
+
+ /* keep the next_drq cache up to date */
+ if (dd->next_drq[data_dir] != NULL) {
+ sector_t last = dd->last_sector[data_dir];
+ sector_t next = dd->next_drq[data_dir]->request->sector;
+ sector_t this = drq->request->sector;
+
+ /*
+ * We can have one of the following 2 situations. If "this"
+ * lands on a + (or L), it is a better "next" candidate.
+ *
+ * ---L+++N---
+ * +++N---L+++
+ */
+ if ((next > last && (this >= last && this < next))
+ || (next < last && (this >= last || this < next)) )
+ /* we have a better "next" drq */
+ dd->next_drq[data_dir] = drq;
+ } else
+ dd->next_drq[data_dir] = drq;
+ /* now add to the rb tree */
drq->rb_key = rq_rb_key(drq->request);
__alias = __deadline_add_drq_rb(dd, drq);
@@ -219,9 +260,10 @@ deadline_del_drq_rb(struct deadline_data
if (dd->next_drq[data_dir] == drq) {
struct rb_node *rbnext = rb_next(&drq->rb_node);
- dd->next_drq[data_dir] = NULL;
if (rbnext)
dd->next_drq[data_dir] = rb_entry_drq(rbnext);
+ else
+ dd->next_drq[data_dir] = deadline_find_first_drq(dd, data_dir);
}
if (ON_RB(&drq->rb_node)) {
@@ -251,24 +293,6 @@ deadline_find_drq_rb(struct deadline_dat
}
/*
- * deadline_find_first_drq finds the first (lowest sector numbered) request
- * for the specified data_dir. Used to sweep back to the start of the disk
- * (1-way elevator) after we process the last (highest sector) request.
- */
-static struct deadline_rq *
-deadline_find_first_drq(struct deadline_data *dd, int data_dir)
-{
- struct rb_node *n = dd->sort_list[data_dir].rb_node;
-
- for (;;) {
- if (n->rb_left == NULL)
- return rb_entry_drq(n);
-
- n = n->rb_left;
- }
-}
-
-/*
* add drq to rbtree and fifo
*/
static inline void
@@ -439,13 +463,12 @@ deadline_move_request(struct deadline_da
const int data_dir = rq_data_dir(drq->request);
struct rb_node *rbnext = rb_next(&drq->rb_node);
- dd->next_drq[READ] = NULL;
- dd->next_drq[WRITE] = NULL;
-
if (rbnext)
dd->next_drq[data_dir] = rb_entry_drq(rbnext);
-
- dd->last_sector = drq->request->sector + drq->request->nr_sectors;
+ else
+ dd->next_drq[data_dir] = deadline_find_first_drq(dd, data_dir);
+
+ dd->last_sector[data_dir] = drq->request->sector + drq->request->nr_sectors;
/*
* take it off the sort and fifo list, move
@@ -485,20 +508,14 @@ static int deadline_dispatch_requests(st
int data_dir, other_dir;
/*
- * batches are currently reads XOR writes
+ * batches are reads XOR writes
*/
- drq = NULL;
-
- if (dd->next_drq[READ])
- drq = dd->next_drq[READ];
-
- if (dd->next_drq[WRITE])
- drq = dd->next_drq[WRITE];
+ drq = dd->next_drq[dd->batch_data_dir];
if (drq) {
/* we have a "next request" */
- if (dd->last_sector != drq->request->sector)
+ if (dd->last_sector[dd->batch_data_dir] != drq->request->sector)
/* end the batch on a non sequential request */
dd->batching += dd->fifo_batch;
@@ -511,6 +528,8 @@ static int deadline_dispatch_requests(st
* at this point we are not running a batch. select the appropriate
* data direction (read / write)
*/
+
+ dd->batching = 0; /* start a new batch */
if (reads) {
BUG_ON(RB_EMPTY(&dd->sort_list[READ]));
@@ -518,7 +537,7 @@ static int deadline_dispatch_requests(st
if (writes && (dd->starved++ >= dd->writes_starved))
goto dispatch_writes;
- data_dir = READ;
+ data_dir = dd->batch_data_dir = READ;
other_dir = WRITE;
goto dispatch_find_request;
@@ -534,7 +553,7 @@ dispatch_writes:
dd->starved = 0;
- data_dir = WRITE;
+ data_dir = dd->batch_data_dir = WRITE;
other_dir = READ;
goto dispatch_find_request;
@@ -546,26 +565,13 @@ dispatch_find_request:
/*
* we are not running a batch, find best request for selected data_dir
*/
- if (deadline_check_fifo(dd, data_dir)) {
+ if (deadline_check_fifo(dd, data_dir))
/* An expired request exists - satisfy it */
- dd->batching = 0;
drq = list_entry_fifo(dd->fifo_list[data_dir].next);
-
- } else if (dd->next_drq[data_dir]) {
- /*
- * The last req was the same dir and we have a next request in
- * sort order. No expired requests so continue on from here.
- */
+
+ else
+ /* No expired requests, get the next in sort order */
drq = dd->next_drq[data_dir];
- } else {
- /*
- * The last req was the other direction or we have run out of
- * higher-sectored requests. Go back to the lowest sectored
- * request (1 way elevator) and start a new batch.
- */
- dd->batching = 0;
- drq = deadline_find_first_drq(dd, data_dir);
- }
dispatch_request:
/*
_