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[PATCH] cfq-iosched: use last service point as the fairness criteria
Right now we use slice_start, which gives async queues an unfair advantage. Chance that to service_last, and base the resorter on that. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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parent
b0b8d74941
commit
99f9628aba
1 changed files with 34 additions and 14 deletions
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@ -146,9 +146,9 @@ struct cfq_queue {
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/* fifo list of requests in sort_list */
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/* fifo list of requests in sort_list */
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struct list_head fifo;
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struct list_head fifo;
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unsigned long slice_start;
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unsigned long slice_end;
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unsigned long slice_end;
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unsigned long slice_left;
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unsigned long slice_left;
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unsigned long service_last;
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/* number of requests that are on the dispatch list */
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/* number of requests that are on the dispatch list */
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int on_dispatch[2];
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int on_dispatch[2];
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@ -355,7 +355,8 @@ cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
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static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
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static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
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{
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{
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struct cfq_data *cfqd = cfqq->cfqd;
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struct cfq_data *cfqd = cfqq->cfqd;
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struct list_head *list;
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struct list_head *list, *n;
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struct cfq_queue *__cfqq;
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/*
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/*
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* Resorting requires the cfqq to be on the RR list already.
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* Resorting requires the cfqq to be on the RR list already.
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@ -383,15 +384,13 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
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list = &cfqd->rr_list[cfqq->ioprio];
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list = &cfqd->rr_list[cfqq->ioprio];
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}
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}
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/*
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* If this queue was preempted or is new (never been serviced), let
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* it be added first for fairness but beind other new queues.
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* Otherwise, just add to the back of the list.
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*/
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if (preempted || cfq_cfqq_queue_new(cfqq)) {
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if (preempted || cfq_cfqq_queue_new(cfqq)) {
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struct list_head *n = list;
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/*
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struct cfq_queue *__cfqq;
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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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while (n->next != list) {
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__cfqq = list_entry_cfqq(n->next);
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__cfqq = list_entry_cfqq(n->next);
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if (!cfq_cfqq_queue_new(__cfqq))
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if (!cfq_cfqq_queue_new(__cfqq))
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@ -399,11 +398,32 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
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n = n->next;
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n = n->next;
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}
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}
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list_add_tail(&cfqq->cfq_list, n);
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list = n;
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} else if (!cfq_cfqq_class_sync(cfqq)) {
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}
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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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list_add_tail(&cfqq->cfq_list, list);
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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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*/
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n = list;
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while ((n = n->prev) != list) {
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struct cfq_queue *__cfqq = list_entry_cfqq(n);
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if (!cfq_cfqq_class_sync(cfqq) || !__cfqq->service_last)
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break;
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if (time_before(__cfqq->service_last, cfqq->service_last))
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break;
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}
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list_add(&cfqq->cfq_list, n);
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}
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}
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}
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/*
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/*
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@ -608,7 +628,6 @@ __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
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*/
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*/
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del_timer(&cfqd->idle_class_timer);
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del_timer(&cfqd->idle_class_timer);
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cfqq->slice_start = jiffies;
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cfqq->slice_end = 0;
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cfqq->slice_end = 0;
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cfqq->slice_left = 0;
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cfqq->slice_left = 0;
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cfq_clear_cfqq_must_alloc_slice(cfqq);
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cfq_clear_cfqq_must_alloc_slice(cfqq);
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@ -1688,6 +1707,7 @@ static void cfq_completed_request(request_queue_t *q, struct request *rq)
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WARN_ON(!cfqq->on_dispatch[sync]);
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WARN_ON(!cfqq->on_dispatch[sync]);
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cfqd->rq_in_driver--;
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cfqd->rq_in_driver--;
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cfqq->on_dispatch[sync]--;
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cfqq->on_dispatch[sync]--;
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cfqq->service_last = now;
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if (!cfq_class_idle(cfqq))
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if (!cfq_class_idle(cfqq))
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cfqd->last_end_request = now;
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cfqd->last_end_request = now;
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