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[PATCH] deadline-iosched: remove elevator private drq request type
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A big win, we now save an allocation/free on each request! With the
previous rb/hash abstractions, we can just reuse queuelist/donelist
for the FIFO data and be done with it.

Signed-off-by: Jens Axboe <axboe@suse.de>
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Jens Axboe authored and Jens Axboe committed Sep 30, 2006
1 parent 9e2585a commit 8840faa
Showing 1 changed file with 52 additions and 142 deletions.
194 changes: 52 additions & 142 deletions block/deadline-iosched.c
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,7 @@ struct deadline_data {
/*
* next in sort order. read, write or both are NULL
*/
struct deadline_rq *next_drq[2];
struct request *next_rq[2];
unsigned int batching; /* number of sequential requests made */
sector_t last_sector; /* head position */
unsigned int starved; /* times reads have starved writes */
Expand All @@ -49,92 +49,69 @@ struct deadline_data {
int fifo_batch;
int writes_starved;
int front_merges;

mempool_t *drq_pool;
};

/*
* pre-request data.
*/
struct deadline_rq {
struct request *request;

/*
* expire fifo
*/
struct list_head fifo;
unsigned long expires;
};

static void deadline_move_request(struct deadline_data *dd, struct deadline_rq *drq);

static kmem_cache_t *drq_pool;

#define RQ_DATA(rq) ((struct deadline_rq *) (rq)->elevator_private)
static void deadline_move_request(struct deadline_data *, struct request *);

#define RQ_RB_ROOT(dd, rq) (&(dd)->sort_list[rq_data_dir((rq))])
#define DRQ_RB_ROOT(dd, drq) RQ_RB_ROOT((drq)->request)

static void
deadline_add_drq_rb(struct deadline_data *dd, struct request *rq)
deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
{
struct rb_root *root = RQ_RB_ROOT(dd, rq);
struct request *__alias;

retry:
__alias = elv_rb_add(root, rq);
if (unlikely(__alias)) {
deadline_move_request(dd, RQ_DATA(__alias));
deadline_move_request(dd, __alias);
goto retry;
}
}

static inline void
deadline_del_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
{
struct request *rq = drq->request;
const int data_dir = rq_data_dir(rq);

if (dd->next_drq[data_dir] == drq) {
if (dd->next_rq[data_dir] == rq) {
struct rb_node *rbnext = rb_next(&rq->rb_node);

dd->next_drq[data_dir] = NULL;
dd->next_rq[data_dir] = NULL;
if (rbnext)
dd->next_drq[data_dir] = RQ_DATA(rb_entry_rq(rbnext));
dd->next_rq[data_dir] = rb_entry_rq(rbnext);
}

elv_rb_del(RQ_RB_ROOT(dd, rq), rq);
}

/*
* add drq to rbtree and fifo
* add rq to rbtree and fifo
*/
static void
deadline_add_request(struct request_queue *q, struct request *rq)
{
struct deadline_data *dd = q->elevator->elevator_data;
struct deadline_rq *drq = RQ_DATA(rq);
const int data_dir = rq_data_dir(drq->request);
const int data_dir = rq_data_dir(rq);

deadline_add_drq_rb(dd, rq);
deadline_add_rq_rb(dd, rq);

/*
* set expire time (only used for reads) and add to fifo list
*/
drq->expires = jiffies + dd->fifo_expire[data_dir];
list_add_tail(&drq->fifo, &dd->fifo_list[data_dir]);
rq_set_fifo_time(rq, jiffies + dd->fifo_expire[data_dir]);
list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
}

/*
* remove rq from rbtree and fifo.
*/
static void deadline_remove_request(request_queue_t *q, struct request *rq)
{
struct deadline_rq *drq = RQ_DATA(rq);
struct deadline_data *dd = q->elevator->elevator_data;

list_del_init(&drq->fifo);
deadline_del_drq_rb(dd, drq);
rq_fifo_clear(rq);
deadline_del_rq_rb(dd, rq);
}

static int
Expand Down Expand Up @@ -177,28 +154,22 @@ static void deadline_merged_request(request_queue_t *q, struct request *req,
*/
if (type == ELEVATOR_FRONT_MERGE) {
elv_rb_del(RQ_RB_ROOT(dd, req), req);
deadline_add_drq_rb(dd, req);
deadline_add_rq_rb(dd, req);
}
}

static void
deadline_merged_requests(request_queue_t *q, struct request *req,
struct request *next)
{
struct deadline_rq *drq = RQ_DATA(req);
struct deadline_rq *dnext = RQ_DATA(next);

BUG_ON(!drq);
BUG_ON(!dnext);

/*
* if dnext expires before drq, assign its expire time to drq
* and move into dnext position (dnext will be deleted) in fifo
* if next expires before rq, assign its expire time to rq
* and move into next position (next will be deleted) in fifo
*/
if (!list_empty(&drq->fifo) && !list_empty(&dnext->fifo)) {
if (time_before(dnext->expires, drq->expires)) {
list_move(&drq->fifo, &dnext->fifo);
drq->expires = dnext->expires;
if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
if (time_before(rq_fifo_time(next), rq_fifo_time(req))) {
list_move(&req->queuelist, &next->queuelist);
rq_set_fifo_time(req, rq_fifo_time(next));
}
}

Expand All @@ -212,53 +183,50 @@ deadline_merged_requests(request_queue_t *q, struct request *req,
* move request from sort list to dispatch queue.
*/
static inline void
deadline_move_to_dispatch(struct deadline_data *dd, struct deadline_rq *drq)
deadline_move_to_dispatch(struct deadline_data *dd, struct request *rq)
{
request_queue_t *q = drq->request->q;
request_queue_t *q = rq->q;

deadline_remove_request(q, drq->request);
elv_dispatch_add_tail(q, drq->request);
deadline_remove_request(q, rq);
elv_dispatch_add_tail(q, rq);
}

/*
* move an entry to dispatch queue
*/
static void
deadline_move_request(struct deadline_data *dd, struct deadline_rq *drq)
deadline_move_request(struct deadline_data *dd, struct request *rq)
{
struct request *rq = drq->request;
const int data_dir = rq_data_dir(rq);
struct rb_node *rbnext = rb_next(&rq->rb_node);

dd->next_drq[READ] = NULL;
dd->next_drq[WRITE] = NULL;
dd->next_rq[READ] = NULL;
dd->next_rq[WRITE] = NULL;

if (rbnext)
dd->next_drq[data_dir] = RQ_DATA(rb_entry_rq(rbnext));
dd->next_rq[data_dir] = rb_entry_rq(rbnext);

dd->last_sector = drq->request->sector + drq->request->nr_sectors;
dd->last_sector = rq->sector + rq->nr_sectors;

/*
* take it off the sort and fifo list, move
* to dispatch queue
*/
deadline_move_to_dispatch(dd, drq);
deadline_move_to_dispatch(dd, rq);
}

#define list_entry_fifo(ptr) list_entry((ptr), struct deadline_rq, fifo)

/*
* deadline_check_fifo returns 0 if there are no expired reads on the fifo,
* 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
*/
static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
{
struct deadline_rq *drq = list_entry_fifo(dd->fifo_list[ddir].next);
struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);

/*
* drq is expired!
* rq is expired!
*/
if (time_after(jiffies, drq->expires))
if (time_after(jiffies, rq_fifo_time(rq)))
return 1;

return 0;
Expand All @@ -273,21 +241,21 @@ static int deadline_dispatch_requests(request_queue_t *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 deadline_rq *drq;
struct request *rq;
int data_dir;

/*
* batches are currently reads XOR writes
*/
if (dd->next_drq[WRITE])
drq = dd->next_drq[WRITE];
if (dd->next_rq[WRITE])
rq = dd->next_rq[WRITE];
else
drq = dd->next_drq[READ];
rq = dd->next_rq[READ];

if (drq) {
if (rq) {
/* we have a "next request" */

if (dd->last_sector != drq->request->sector)
if (dd->last_sector != rq->sector)
/* end the batch on a non sequential request */
dd->batching += dd->fifo_batch;

Expand Down Expand Up @@ -336,34 +304,33 @@ static int deadline_dispatch_requests(request_queue_t *q, int force)
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);
rq = rq_entry_fifo(dd->fifo_list[data_dir].next);

} else if (dd->next_drq[data_dir]) {
} else if (dd->next_rq[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.
*/
drq = dd->next_drq[data_dir];
rq = dd->next_rq[data_dir];
} else {
struct rb_node *n;

struct rb_node *node;
/*
* 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;
n = rb_first(&dd->sort_list[data_dir]);
if (n)
drq = RQ_DATA(rb_entry_rq(n));
node = rb_first(&dd->sort_list[data_dir]);
if (node)
rq = rb_entry_rq(node);
}

dispatch_request:
/*
* drq is the selected appropriate request.
* rq is the selected appropriate request.
*/
dd->batching++;
deadline_move_request(dd, drq);
deadline_move_request(dd, rq);

return 1;
}
Expand All @@ -383,33 +350,21 @@ static void deadline_exit_queue(elevator_t *e)
BUG_ON(!list_empty(&dd->fifo_list[READ]));
BUG_ON(!list_empty(&dd->fifo_list[WRITE]));

mempool_destroy(dd->drq_pool);
kfree(dd);
}

/*
* initialize elevator private data (deadline_data), and alloc a drq for
* each request on the free lists
* initialize elevator private data (deadline_data).
*/
static void *deadline_init_queue(request_queue_t *q, elevator_t *e)
{
struct deadline_data *dd;

if (!drq_pool)
return NULL;

dd = kmalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
if (!dd)
return NULL;
memset(dd, 0, sizeof(*dd));

dd->drq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
mempool_free_slab, drq_pool, q->node);
if (!dd->drq_pool) {
kfree(dd);
return NULL;
}

INIT_LIST_HEAD(&dd->fifo_list[READ]);
INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
dd->sort_list[READ] = RB_ROOT;
Expand All @@ -422,36 +377,6 @@ static void *deadline_init_queue(request_queue_t *q, elevator_t *e)
return dd;
}

static void deadline_put_request(request_queue_t *q, struct request *rq)
{
struct deadline_data *dd = q->elevator->elevator_data;
struct deadline_rq *drq = RQ_DATA(rq);

mempool_free(drq, dd->drq_pool);
rq->elevator_private = NULL;
}

static int
deadline_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
gfp_t gfp_mask)
{
struct deadline_data *dd = q->elevator->elevator_data;
struct deadline_rq *drq;

drq = mempool_alloc(dd->drq_pool, gfp_mask);
if (drq) {
memset(drq, 0, sizeof(*drq));
drq->request = rq;

INIT_LIST_HEAD(&drq->fifo);

rq->elevator_private = drq;
return 0;
}

return 1;
}

/*
* sysfs parts below
*/
Expand Down Expand Up @@ -533,8 +458,6 @@ static struct elevator_type iosched_deadline = {
.elevator_queue_empty_fn = deadline_queue_empty,
.elevator_former_req_fn = elv_rb_former_request,
.elevator_latter_req_fn = elv_rb_latter_request,
.elevator_set_req_fn = deadline_set_request,
.elevator_put_req_fn = deadline_put_request,
.elevator_init_fn = deadline_init_queue,
.elevator_exit_fn = deadline_exit_queue,
},
Expand All @@ -546,24 +469,11 @@ static struct elevator_type iosched_deadline = {

static int __init deadline_init(void)
{
int ret;

drq_pool = kmem_cache_create("deadline_drq", sizeof(struct deadline_rq),
0, 0, NULL, NULL);

if (!drq_pool)
return -ENOMEM;

ret = elv_register(&iosched_deadline);
if (ret)
kmem_cache_destroy(drq_pool);

return ret;
return elv_register(&iosched_deadline);
}

static void __exit deadline_exit(void)
{
kmem_cache_destroy(drq_pool);
elv_unregister(&iosched_deadline);
}

Expand Down

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