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cfq-iosched: minor updates

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- 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>
This commit is contained in:
Jens Axboe 2007-04-17 12:47:55 +02:00 committed by Jens Axboe
parent 6d048f5310
commit 1afba0451c
1 changed files with 18 additions and 63 deletions
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81
block/cfq-iosched.c
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@ -70,7 +70,6 @@ struct cfq_data {
* rr list of queues with requests and the count of them
*/
struct list_head rr_list[CFQ_PRIO_LISTS];
struct list_head busy_rr;
struct list_head cur_rr;
struct list_head idle_rr;
unsigned long cur_rr_tick;
@ -410,59 +409,18 @@ cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
static void cfq_resort_be_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq,
int preempted)
{
struct list_head *list, *n;
struct cfq_queue *__cfqq;
int add_tail = 0;
if (!cfq_cfqq_sync(cfqq))
list_add_tail(&cfqq->cfq_list, &cfqd->rr_list[cfqq->ioprio]);
else {
struct list_head *n = &cfqd->rr_list[cfqq->ioprio];
/*
* if cfqq has requests in flight, don't allow it to be
* found in cfq_set_active_queue before it has finished them.
* this is done to increase fairness between a process that
* has lots of io pending vs one that only generates one
* sporadically or synchronously
*/
if (cfqq->dispatched)
list = &cfqd->busy_rr;
else if (cfqq->ioprio == (cfqd->cur_prio + 1) &&
cfq_cfqq_sync(cfqq) &&
(time_before(cfqd->prio_time, cfqq->service_last) ||
cfq_cfqq_queue_new(cfqq) || preempted)) {
list = &cfqd->cur_rr;
add_tail = 1;
} else
list = &cfqd->rr_list[cfqq->ioprio];
if (!cfq_cfqq_sync(cfqq) || add_tail) {
/*
* async queue always goes to the end. this wont be overly
* unfair to writes, as the sort of the sync queue wont be
* allowed to pass the async queue again.
*/
list_add_tail(&cfqq->cfq_list, list);
} else if (preempted || cfq_cfqq_queue_new(cfqq)) {
/*
* If this queue was preempted or is new (never been serviced),
* let it be added first for fairness but beind other new
* queues.
*/
n = list;
while (n->next != list) {
__cfqq = list_entry_cfqq(n->next);
if (!cfq_cfqq_queue_new(__cfqq))
break;
n = n->next;
}
list_add(&cfqq->cfq_list, n);
} else {
/*
* sort by last service, but don't cross a new or async
* queue. we don't cross a new queue because it hasn't been
* service before, and we don't cross an async queue because
* it gets added to the end on expire.
* queue. we don't cross a new queue because it hasn't
* been service before, and we don't cross an async
* queue because it gets added to the end on expire.
*/
n = list;
while ((n = n->prev) != list) {
while ((n = n->prev) != &cfqd->rr_list[cfqq->ioprio]) {
struct cfq_queue *__c = list_entry_cfqq(n);
if (!cfq_cfqq_sync(__c) || !__c->service_last)
@ -725,6 +683,7 @@ __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
cfq_clear_cfqq_must_alloc_slice(cfqq);
cfq_clear_cfqq_fifo_expire(cfqq);
cfq_mark_cfqq_slice_new(cfqq);
cfq_clear_cfqq_queue_new(cfqq);
cfqq->rr_tick = cfqd->cur_rr_tick;
}
@ -743,7 +702,6 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
cfq_clear_cfqq_must_dispatch(cfqq);
cfq_clear_cfqq_wait_request(cfqq);
cfq_clear_cfqq_queue_new(cfqq);
/*
* store what was left of this slice, if the queue idled out
@ -845,13 +803,15 @@ static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
static struct cfq_queue *cfq_get_best_queue(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq = NULL, *__cfqq;
sector_t best = -1, dist;
sector_t best = -1, first = -1, dist;
list_for_each_entry(__cfqq, &cfqd->cur_rr, cfq_list) {
if (!__cfqq->next_rq || !cfq_cfqq_sync(__cfqq))
continue;
dist = cfq_dist_from_last(cfqd, __cfqq->next_rq);
if (first == -1)
first = dist;
if (dist < best) {
best = dist;
cfqq = __cfqq;
@ -859,9 +819,11 @@ static struct cfq_queue *cfq_get_best_queue(struct cfq_data *cfqd)
}
/*
* Only async queue(s) available, grab first entry
* Only async queue(s) available, grab first entry. Do the same
* if the difference between the first and best isn't more than
* twice, to obey fairness.
*/
if (!cfqq)
if (!cfqq || (best && first != best && ((first / best) < 4)))
cfqq = list_entry_cfqq(cfqd->cur_rr.next);
return cfqq;
@ -878,12 +840,6 @@ static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
* are spliced
*/
cfqq = cfq_get_best_queue(cfqd);
} else if (!list_empty(&cfqd->busy_rr)) {
/*
* If no new queues are available, check if the busy list has
* some before falling back to idle io.
*/
cfqq = list_entry_cfqq(cfqd->busy_rr.next);
} else if (!list_empty(&cfqd->idle_rr)) {
/*
* if we have idle queues and no rt or be queues had pending
@ -1004,7 +960,8 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
/*
* See if this prio level has a good candidate
*/
if (cfq_close_cooperator(cfqd, cfqq))
if (cfq_close_cooperator(cfqd, cfqq) &&
(sample_valid(cic->ttime_samples) && cic->ttime_mean > 2))
return;
cfq_mark_cfqq_must_dispatch(cfqq);
@ -1184,7 +1141,6 @@ cfq_forced_dispatch(struct cfq_data *cfqd)
for (i = 0; i < CFQ_PRIO_LISTS; i++)
dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr);
dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
@ -2174,7 +2130,6 @@ static void *cfq_init_queue(request_queue_t *q)
for (i = 0; i < CFQ_PRIO_LISTS; i++)
INIT_LIST_HEAD(&cfqd->rr_list[i]);
INIT_LIST_HEAD(&cfqd->busy_rr);
INIT_LIST_HEAD(&cfqd->cur_rr);
INIT_LIST_HEAD(&cfqd->idle_rr);
INIT_LIST_HEAD(&cfqd->cic_list);