cfq-iosched: minor updates
- Move the queue_new flag clear to when the queue is selected - Only select the non-first queue in cfq_get_best_queue(), if there's a substantial difference between the best and first. - Get rid of ->busy_rr - Only select a close cooperator, if the current queue is known to take a while to "think". Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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@ -70,7 +70,6 @@ struct cfq_data {
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* rr list of queues with requests and the count of them
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*/
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struct list_head rr_list[CFQ_PRIO_LISTS];
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struct list_head busy_rr;
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struct list_head cur_rr;
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struct list_head idle_rr;
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unsigned long cur_rr_tick;
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@ -410,59 +409,18 @@ cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
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static void cfq_resort_be_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq,
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int preempted)
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{
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struct list_head *list, *n;
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struct cfq_queue *__cfqq;
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int add_tail = 0;
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if (!cfq_cfqq_sync(cfqq))
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list_add_tail(&cfqq->cfq_list, &cfqd->rr_list[cfqq->ioprio]);
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else {
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struct list_head *n = &cfqd->rr_list[cfqq->ioprio];
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/*
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* if cfqq has requests in flight, don't allow it to be
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* found in cfq_set_active_queue before it has finished them.
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* this is done to increase fairness between a process that
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* has lots of io pending vs one that only generates one
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* sporadically or synchronously
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*/
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if (cfqq->dispatched)
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list = &cfqd->busy_rr;
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else if (cfqq->ioprio == (cfqd->cur_prio + 1) &&
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cfq_cfqq_sync(cfqq) &&
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(time_before(cfqd->prio_time, cfqq->service_last) ||
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cfq_cfqq_queue_new(cfqq) || preempted)) {
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list = &cfqd->cur_rr;
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add_tail = 1;
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} else
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list = &cfqd->rr_list[cfqq->ioprio];
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if (!cfq_cfqq_sync(cfqq) || add_tail) {
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/*
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* async queue always goes to the end. this wont be overly
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* unfair to writes, as the sort of the sync queue wont be
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* allowed to pass the async queue again.
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*/
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list_add_tail(&cfqq->cfq_list, list);
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} else if (preempted || cfq_cfqq_queue_new(cfqq)) {
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/*
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* If this queue was preempted or is new (never been serviced),
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* let it be added first for fairness but beind other new
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* queues.
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*/
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n = list;
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while (n->next != list) {
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__cfqq = list_entry_cfqq(n->next);
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if (!cfq_cfqq_queue_new(__cfqq))
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break;
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n = n->next;
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}
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list_add(&cfqq->cfq_list, n);
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} else {
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/*
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* sort by last service, but don't cross a new or async
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* queue. we don't cross a new queue because it hasn't been
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* service before, and we don't cross an async queue because
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* it gets added to the end on expire.
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* queue. we don't cross a new queue because it hasn't
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* been service before, and we don't cross an async
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* queue because it gets added to the end on expire.
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*/
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n = list;
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while ((n = n->prev) != list) {
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while ((n = n->prev) != &cfqd->rr_list[cfqq->ioprio]) {
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struct cfq_queue *__c = list_entry_cfqq(n);
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if (!cfq_cfqq_sync(__c) || !__c->service_last)
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@ -725,6 +683,7 @@ __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
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cfq_clear_cfqq_must_alloc_slice(cfqq);
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cfq_clear_cfqq_fifo_expire(cfqq);
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cfq_mark_cfqq_slice_new(cfqq);
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cfq_clear_cfqq_queue_new(cfqq);
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cfqq->rr_tick = cfqd->cur_rr_tick;
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}
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@ -743,7 +702,6 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
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cfq_clear_cfqq_must_dispatch(cfqq);
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cfq_clear_cfqq_wait_request(cfqq);
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cfq_clear_cfqq_queue_new(cfqq);
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/*
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* store what was left of this slice, if the queue idled out
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@ -845,13 +803,15 @@ static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
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static struct cfq_queue *cfq_get_best_queue(struct cfq_data *cfqd)
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{
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struct cfq_queue *cfqq = NULL, *__cfqq;
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sector_t best = -1, dist;
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sector_t best = -1, first = -1, dist;
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list_for_each_entry(__cfqq, &cfqd->cur_rr, cfq_list) {
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if (!__cfqq->next_rq || !cfq_cfqq_sync(__cfqq))
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continue;
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dist = cfq_dist_from_last(cfqd, __cfqq->next_rq);
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if (first == -1)
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first = dist;
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if (dist < best) {
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best = dist;
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cfqq = __cfqq;
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@ -859,9 +819,11 @@ static struct cfq_queue *cfq_get_best_queue(struct cfq_data *cfqd)
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}
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/*
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* Only async queue(s) available, grab first entry
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* Only async queue(s) available, grab first entry. Do the same
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* if the difference between the first and best isn't more than
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* twice, to obey fairness.
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*/
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if (!cfqq)
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if (!cfqq || (best && first != best && ((first / best) < 4)))
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cfqq = list_entry_cfqq(cfqd->cur_rr.next);
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return cfqq;
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@ -878,12 +840,6 @@ static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
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* are spliced
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*/
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cfqq = cfq_get_best_queue(cfqd);
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} else if (!list_empty(&cfqd->busy_rr)) {
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/*
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* If no new queues are available, check if the busy list has
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* some before falling back to idle io.
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*/
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cfqq = list_entry_cfqq(cfqd->busy_rr.next);
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} else if (!list_empty(&cfqd->idle_rr)) {
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/*
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* if we have idle queues and no rt or be queues had pending
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@ -1004,7 +960,8 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
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/*
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* See if this prio level has a good candidate
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*/
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if (cfq_close_cooperator(cfqd, cfqq))
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if (cfq_close_cooperator(cfqd, cfqq) &&
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(sample_valid(cic->ttime_samples) && cic->ttime_mean > 2))
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return;
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cfq_mark_cfqq_must_dispatch(cfqq);
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@ -1184,7 +1141,6 @@ cfq_forced_dispatch(struct cfq_data *cfqd)
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for (i = 0; i < CFQ_PRIO_LISTS; i++)
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dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
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dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr);
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dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
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dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
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@ -2174,7 +2130,6 @@ static void *cfq_init_queue(request_queue_t *q)
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for (i = 0; i < CFQ_PRIO_LISTS; i++)
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INIT_LIST_HEAD(&cfqd->rr_list[i]);
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INIT_LIST_HEAD(&cfqd->busy_rr);
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INIT_LIST_HEAD(&cfqd->cur_rr);
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INIT_LIST_HEAD(&cfqd->idle_rr);
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INIT_LIST_HEAD(&cfqd->cic_list);
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