[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: Tejun Heo <htejun@gmail.com> Signed-off-by: Jens Axboe <axboe@suse.de>
This commit is contained in:
Tejun Heo
Jens Axboe
parent
9f155b9802
commit
ef9be1d336
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@ -182,6 +182,9 @@ struct as_rq {
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static kmem_cache_t *arq_pool;
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static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq);
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static void as_antic_stop(struct as_data *ad);
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/*
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* IO Context helper functions
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*/
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@ -370,7 +373,7 @@ static struct as_rq *as_find_first_arq(struct as_data *ad, int data_dir)
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* existing request against the same sector), which can happen when using
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* direct IO, then return the alias.
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*/
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static struct as_rq *as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
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static struct as_rq *__as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
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{
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struct rb_node **p = &ARQ_RB_ROOT(ad, arq)->rb_node;
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struct rb_node *parent = NULL;
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@ -397,6 +400,16 @@ static struct as_rq *as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
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return NULL;
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}
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static void as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
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{
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struct as_rq *alias;
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while ((unlikely(alias = __as_add_arq_rb(ad, arq)))) {
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as_move_to_dispatch(ad, alias);
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as_antic_stop(ad);
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}
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}
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static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq)
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{
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if (!ON_RB(&arq->rb_node)) {
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@ -1133,23 +1146,6 @@ static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
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/*
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* take it off the sort and fifo list, add to dispatch queue
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*/
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while (!list_empty(&rq->queuelist)) {
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struct request *__rq = list_entry_rq(rq->queuelist.next);
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struct as_rq *__arq = RQ_DATA(__rq);
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list_del(&__rq->queuelist);
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elv_dispatch_add_tail(ad->q, __rq);
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if (__arq->io_context && __arq->io_context->aic)
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atomic_inc(&__arq->io_context->aic->nr_dispatched);
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WARN_ON(__arq->state != AS_RQ_QUEUED);
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__arq->state = AS_RQ_DISPATCHED;
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ad->nr_dispatched++;
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}
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as_remove_queued_request(ad->q, rq);
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WARN_ON(arq->state != AS_RQ_QUEUED);
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@ -1325,42 +1321,6 @@ fifo_expired:
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return 1;
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}
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/*
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* Add arq to a list behind alias
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*/
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static inline void
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as_add_aliased_request(struct as_data *ad, struct as_rq *arq,
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struct as_rq *alias)
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{
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struct request *req = arq->request;
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struct list_head *insert = alias->request->queuelist.prev;
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/*
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* Transfer list of aliases
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*/
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while (!list_empty(&req->queuelist)) {
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struct request *__rq = list_entry_rq(req->queuelist.next);
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struct as_rq *__arq = RQ_DATA(__rq);
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list_move_tail(&__rq->queuelist, &alias->request->queuelist);
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WARN_ON(__arq->state != AS_RQ_QUEUED);
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}
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/*
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* Another request with the same start sector on the rbtree.
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* Link this request to that sector. They are untangled in
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* as_move_to_dispatch
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*/
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list_add(&arq->request->queuelist, insert);
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/*
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* Don't want to have to handle merges.
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*/
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as_del_arq_hash(arq);
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arq->request->flags |= REQ_NOMERGE;
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}
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/*
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* add arq to rbtree and fifo
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*/
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@ -1368,7 +1328,6 @@ static void as_add_request(request_queue_t *q, struct request *rq)
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{
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struct as_data *ad = q->elevator->elevator_data;
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struct as_rq *arq = RQ_DATA(rq);
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struct as_rq *alias;
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int data_dir;
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arq->state = AS_RQ_NEW;
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@ -1387,33 +1346,17 @@ static void as_add_request(request_queue_t *q, struct request *rq)
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atomic_inc(&arq->io_context->aic->nr_queued);
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}
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alias = as_add_arq_rb(ad, arq);
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if (!alias) {
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/*
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* set expire time (only used for reads) and add to fifo list
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*/
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arq->expires = jiffies + ad->fifo_expire[data_dir];
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list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]);
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as_add_arq_rb(ad, arq);
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if (rq_mergeable(arq->request))
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as_add_arq_hash(ad, arq);
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if (rq_mergeable(arq->request))
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as_add_arq_hash(ad, arq);
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as_update_arq(ad, arq); /* keep state machine up to date */
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} else {
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as_add_aliased_request(ad, arq, alias);
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/*
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* have we been anticipating this request?
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* or does it come from the same process as the one we are
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* anticipating for?
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*/
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if (ad->antic_status == ANTIC_WAIT_REQ
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|| ad->antic_status == ANTIC_WAIT_NEXT) {
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if (as_can_break_anticipation(ad, arq))
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as_antic_stop(ad);
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}
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}
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/*
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* set expire time (only used for reads) and add to fifo list
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*/
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arq->expires = jiffies + ad->fifo_expire[data_dir];
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list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]);
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as_update_arq(ad, arq); /* keep state machine up to date */
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arq->state = AS_RQ_QUEUED;
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}
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@ -1536,23 +1479,8 @@ static void as_merged_request(request_queue_t *q, struct request *req)
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* if the merge was a front merge, we need to reposition request
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*/
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if (rq_rb_key(req) != arq->rb_key) {
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struct as_rq *alias, *next_arq = NULL;
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if (ad->next_arq[arq->is_sync] == arq)
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next_arq = as_find_next_arq(ad, arq);
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/*
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* Note! We should really be moving any old aliased requests
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* off this request and try to insert them into the rbtree. We
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* currently don't bother. Ditto the next function.
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*/
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as_del_arq_rb(ad, arq);
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if ((alias = as_add_arq_rb(ad, arq))) {
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list_del_init(&arq->fifo);
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as_add_aliased_request(ad, arq, alias);
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if (next_arq)
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ad->next_arq[arq->is_sync] = next_arq;
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}
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as_add_arq_rb(ad, arq);
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/*
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* Note! At this stage of this and the next function, our next
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* request may not be optimal - eg the request may have "grown"
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@ -1579,18 +1507,8 @@ static void as_merged_requests(request_queue_t *q, struct request *req,
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as_add_arq_hash(ad, arq);
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if (rq_rb_key(req) != arq->rb_key) {
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struct as_rq *alias, *next_arq = NULL;
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if (ad->next_arq[arq->is_sync] == arq)
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next_arq = as_find_next_arq(ad, arq);
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as_del_arq_rb(ad, arq);
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if ((alias = as_add_arq_rb(ad, arq))) {
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list_del_init(&arq->fifo);
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as_add_aliased_request(ad, arq, alias);
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if (next_arq)
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ad->next_arq[arq->is_sync] = next_arq;
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}
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as_add_arq_rb(ad, arq);
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}
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/*
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@ -1609,18 +1527,6 @@ static void as_merged_requests(request_queue_t *q, struct request *req,
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}
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}
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/*
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* Transfer list of aliases
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*/
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while (!list_empty(&next->queuelist)) {
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struct request *__rq = list_entry_rq(next->queuelist.next);
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struct as_rq *__arq = RQ_DATA(__rq);
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list_move_tail(&__rq->queuelist, &req->queuelist);
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WARN_ON(__arq->state != AS_RQ_QUEUED);
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}
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/*
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* kill knowledge of next, this one is a goner
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*/
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