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Commit ef9be1d3 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

[BLOCK] as-iosched: update alias handling 



Unlike other ioscheds, as-iosched handles alias by chaing them using
rq->queuelist.  As aliased requests are very rare in the first place,
this complicates merge/dispatch handling without meaningful
performance improvement.  This patch updates as-iosched to dump
aliased requests into dispatch queue as other ioscheds do.

Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent 9f155b98

block/as-iosched.c

+25 −119
Original line number Diff line number Diff line
@@ -182,6 +182,9 @@ struct as_rq { 


static kmem_cache_t *arq_pool;



static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq);

static void as_antic_stop(struct as_data *ad);



/*

 * IO Context helper functions

 */
@@ -370,7 +373,7 @@ static struct as_rq *as_find_first_arq(struct as_data *ad, int data_dir) 
 * existing request against the same sector), which can happen when using

 * direct IO, then return the alias.

 */

static struct as_rq *as_add_arq_rb(struct as_data *ad, struct as_rq *arq)

static struct as_rq *__as_add_arq_rb(struct as_data *ad, struct as_rq *arq)

{

	struct rb_node **p = &ARQ_RB_ROOT(ad, arq)->rb_node;

	struct rb_node *parent = NULL;
@@ -397,6 +400,16 @@ static struct as_rq *as_add_arq_rb(struct as_data *ad, struct as_rq *arq) 
	return NULL;

}



static void as_add_arq_rb(struct as_data *ad, struct as_rq *arq)

{

	struct as_rq *alias;



	while ((unlikely(alias = __as_add_arq_rb(ad, arq)))) {

		as_move_to_dispatch(ad, alias);

		as_antic_stop(ad);

	}

}



static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq)

{

	if (!ON_RB(&arq->rb_node)) {
@@ -1133,23 +1146,6 @@ static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq) 
	/*

	 * take it off the sort and fifo list, add to dispatch queue

	 */

	while (!list_empty(&rq->queuelist)) {

		struct request *__rq = list_entry_rq(rq->queuelist.next);

		struct as_rq *__arq = RQ_DATA(__rq);



		list_del(&__rq->queuelist);



		elv_dispatch_add_tail(ad->q, __rq);



		if (__arq->io_context && __arq->io_context->aic)

			atomic_inc(&__arq->io_context->aic->nr_dispatched);



		WARN_ON(__arq->state != AS_RQ_QUEUED);

		__arq->state = AS_RQ_DISPATCHED;



		ad->nr_dispatched++;

	}



	as_remove_queued_request(ad->q, rq);

	WARN_ON(arq->state != AS_RQ_QUEUED);
@@ -1325,42 +1321,6 @@ static int as_dispatch_request(request_queue_t *q, int force) 
	return 1;

}



/*

 * Add arq to a list behind alias

 */

static inline void

as_add_aliased_request(struct as_data *ad, struct as_rq *arq,

				struct as_rq *alias)

{

	struct request  *req = arq->request;

	struct list_head *insert = alias->request->queuelist.prev;



	/*

	 * Transfer list of aliases

	 */

	while (!list_empty(&req->queuelist)) {

		struct request *__rq = list_entry_rq(req->queuelist.next);

		struct as_rq *__arq = RQ_DATA(__rq);



		list_move_tail(&__rq->queuelist, &alias->request->queuelist);



		WARN_ON(__arq->state != AS_RQ_QUEUED);

	}



	/*

	 * Another request with the same start sector on the rbtree.

	 * Link this request to that sector. They are untangled in

	 * as_move_to_dispatch

	 */

	list_add(&arq->request->queuelist, insert);



	/*

	 * Don't want to have to handle merges.

	 */

	as_del_arq_hash(arq);

	arq->request->flags |= REQ_NOMERGE;

}



/*

 * add arq to rbtree and fifo

 */
@@ -1368,7 +1328,6 @@ static void as_add_request(request_queue_t *q, struct request *rq) 
{

	struct as_data *ad = q->elevator->elevator_data;

	struct as_rq *arq = RQ_DATA(rq);

	struct as_rq *alias;

	int data_dir;



	arq->state = AS_RQ_NEW;
@@ -1387,33 +1346,17 @@ static void as_add_request(request_queue_t *q, struct request *rq) 
		atomic_inc(&arq->io_context->aic->nr_queued);

	}



	alias = as_add_arq_rb(ad, arq);

	if (!alias) {

	as_add_arq_rb(ad, arq);

	if (rq_mergeable(arq->request))

		as_add_arq_hash(ad, arq);



	/*

	 * set expire time (only used for reads) and add to fifo list

	 */

	arq->expires = jiffies + ad->fifo_expire[data_dir];

	list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]);



		if (rq_mergeable(arq->request))

			as_add_arq_hash(ad, arq);

	as_update_arq(ad, arq); /* keep state machine up to date */



	} else {

		as_add_aliased_request(ad, arq, alias);



		/*

		 * have we been anticipating this request?

		 * or does it come from the same process as the one we are

		 * anticipating for?

		 */

		if (ad->antic_status == ANTIC_WAIT_REQ

				|| ad->antic_status == ANTIC_WAIT_NEXT) {

			if (as_can_break_anticipation(ad, arq))

				as_antic_stop(ad);

		}

	}



	arq->state = AS_RQ_QUEUED;

}
@@ -1536,23 +1479,8 @@ static void as_merged_request(request_queue_t *q, struct request *req) 
	 * if the merge was a front merge, we need to reposition request

	 */

	if (rq_rb_key(req) != arq->rb_key) {

		struct as_rq *alias, *next_arq = NULL;



		if (ad->next_arq[arq->is_sync] == arq)

			next_arq = as_find_next_arq(ad, arq);



		/*

		 * Note! We should really be moving any old aliased requests

		 * off this request and try to insert them into the rbtree. We

		 * currently don't bother. Ditto the next function.

		 */

		as_del_arq_rb(ad, arq);

		if ((alias = as_add_arq_rb(ad, arq))) {

			list_del_init(&arq->fifo);

			as_add_aliased_request(ad, arq, alias);

			if (next_arq)

				ad->next_arq[arq->is_sync] = next_arq;

		}

		as_add_arq_rb(ad, arq);

		/*

		 * Note! At this stage of this and the next function, our next

		 * request may not be optimal - eg the request may have "grown"
@@ -1579,18 +1507,8 @@ static void as_merged_requests(request_queue_t *q, struct request *req, 
	as_add_arq_hash(ad, arq);



	if (rq_rb_key(req) != arq->rb_key) {

		struct as_rq *alias, *next_arq = NULL;



		if (ad->next_arq[arq->is_sync] == arq)

			next_arq = as_find_next_arq(ad, arq);



		as_del_arq_rb(ad, arq);

		if ((alias = as_add_arq_rb(ad, arq))) {

			list_del_init(&arq->fifo);

			as_add_aliased_request(ad, arq, alias);

			if (next_arq)

				ad->next_arq[arq->is_sync] = next_arq;

		}

		as_add_arq_rb(ad, arq);

	}



	/*
@@ -1609,18 +1527,6 @@ static void as_merged_requests(request_queue_t *q, struct request *req, 
		}

	}



	/*

	 * Transfer list of aliases

	 */

	while (!list_empty(&next->queuelist)) {

		struct request *__rq = list_entry_rq(next->queuelist.next);

		struct as_rq *__arq = RQ_DATA(__rq);



		list_move_tail(&__rq->queuelist, &req->queuelist);



		WARN_ON(__arq->state != AS_RQ_QUEUED);

	}



	/*

	 * kill knowledge of next, this one is a goner

	 */