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Date: Tue, 24 Apr 2007 10:15:31 +0200
From: Jens Axboe <jens.axboe@...cle.com>
To: linux-kernel@...r.kernel.org
Cc: Jens Axboe <jens.axboe@...cle.com>
Subject: [PATCH 3/15] 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@...cle.com>
---
block/cfq-iosched.c | 81 +++++++++++---------------------------------------
1 files changed, 18 insertions(+), 63 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 3883ba8..04fea76 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -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 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;
+ 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];
- 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)
@@ -719,6 +677,7 @@ __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;
}
@@ -737,7 +696,6 @@ __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
@@ -839,13 +797,15 @@ 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;
@@ -853,9 +813,11 @@ 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;
@@ -872,12 +834,6 @@ 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
@@ -998,7 +954,8 @@ 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);
@@ -1178,7 +1135,6 @@ 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);
--
1.5.1.1.190.g74474
-
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