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cfq-iosched: get rid of ->cur_rr and ->cfq_list
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It's only used for preemption now that the IDLE and RT queues also
use the rbtree. If we pass an 'add_front' variable to
cfq_service_tree_add(), we can set ->rb_key to 0 to force insertion
at the front of the tree.

Signed-off-by: Jens Axboe <[email protected]>
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Jens Axboe authored and Jens Axboe committed Apr 30, 2007
1 parent 67e6b49 commit edd75ff
Showing 1 changed file with 32 additions and 55 deletions.
87 changes: 32 additions & 55 deletions block/cfq-iosched.c
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Original file line number Diff line number Diff line change
Expand Up @@ -45,9 +45,6 @@ static int cfq_slice_idle = HZ / 125;
*/
#define CFQ_QHASH_SHIFT 6
#define CFQ_QHASH_ENTRIES (1 << CFQ_QHASH_SHIFT)
#define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash)

#define list_entry_cfqq(ptr) list_entry((ptr), struct cfq_queue, cfq_list)

#define RQ_CIC(rq) ((struct cfq_io_context*)(rq)->elevator_private)
#define RQ_CFQQ(rq) ((rq)->elevator_private2)
Expand Down Expand Up @@ -91,7 +88,6 @@ struct cfq_data {
* rr list of queues with requests and the count of them
*/
struct cfq_rb_root service_tree;
struct list_head cur_rr;
unsigned int busy_queues;

/*
Expand Down Expand Up @@ -146,8 +142,6 @@ struct cfq_queue {
struct hlist_node cfq_hash;
/* hash key */
unsigned int key;
/* member of the rr/busy/cur/idle cfqd list */
struct list_head cfq_list;
/* service_tree member */
struct rb_node rb_node;
/* service_tree key */
Expand Down Expand Up @@ -452,16 +446,19 @@ static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
* we will service the queues.
*/
static void cfq_service_tree_add(struct cfq_data *cfqd,
struct cfq_queue *cfqq)
struct cfq_queue *cfqq, int add_front)
{
struct rb_node **p = &cfqd->service_tree.rb.rb_node;
struct rb_node *parent = NULL;
unsigned long rb_key;
int left;

rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
rb_key += cfqq->slice_resid;
cfqq->slice_resid = 0;
if (!add_front) {
rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
rb_key += cfqq->slice_resid;
cfqq->slice_resid = 0;
} else
rb_key = 0;

if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
/*
Expand Down Expand Up @@ -516,13 +513,13 @@ static void cfq_service_tree_add(struct cfq_data *cfqd,
/*
* Update cfqq's position in the service tree.
*/
static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
/*
* Resorting requires the cfqq to be on the RR list already.
*/
if (cfq_cfqq_on_rr(cfqq))
cfq_service_tree_add(cfqq->cfqd, cfqq);
cfq_service_tree_add(cfqd, cfqq, 0);
}

/*
Expand All @@ -536,7 +533,7 @@ cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
cfq_mark_cfqq_on_rr(cfqq);
cfqd->busy_queues++;

cfq_resort_rr_list(cfqq, 0);
cfq_resort_rr_list(cfqd, cfqq);
}

/*
Expand All @@ -548,7 +545,6 @@ cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
BUG_ON(!cfq_cfqq_on_rr(cfqq));
cfq_clear_cfqq_on_rr(cfqq);
list_del_init(&cfqq->cfq_list);

if (!RB_EMPTY_NODE(&cfqq->rb_node))
cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
Expand Down Expand Up @@ -771,7 +767,7 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
if (timed_out && !cfq_cfqq_slice_new(cfqq))
cfqq->slice_resid = cfqq->slice_end - jiffies;

cfq_resort_rr_list(cfqq, preempted);
cfq_resort_rr_list(cfqd, cfqq);

if (cfqq == cfqd->active_queue)
cfqd->active_queue = NULL;
Expand Down Expand Up @@ -799,31 +795,28 @@ static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted,
*/
static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq = NULL;
struct cfq_queue *cfqq;
struct rb_node *n;

if (!list_empty(&cfqd->cur_rr)) {
/*
* if current list is non-empty, grab first entry.
*/
cfqq = list_entry_cfqq(cfqd->cur_rr.next);
} else if (!RB_EMPTY_ROOT(&cfqd->service_tree.rb)) {
struct rb_node *n = cfq_rb_first(&cfqd->service_tree);
if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
return NULL;

cfqq = rb_entry(n, struct cfq_queue, rb_node);
if (cfq_class_idle(cfqq)) {
unsigned long end;
n = cfq_rb_first(&cfqd->service_tree);
cfqq = rb_entry(n, struct cfq_queue, rb_node);

/*
* if we have idle queues and no rt or be queues had
* pending requests, either allow immediate service if
* the grace period has passed or arm the idle grace
* timer
*/
end = cfqd->last_end_request + CFQ_IDLE_GRACE;
if (time_before(jiffies, end)) {
mod_timer(&cfqd->idle_class_timer, end);
cfqq = NULL;
}
if (cfq_class_idle(cfqq)) {
unsigned long end;

/*
* if we have idle queues and no rt or be queues had
* pending requests, either allow immediate service if
* the grace period has passed or arm the idle grace
* timer
*/
end = cfqd->last_end_request + CFQ_IDLE_GRACE;
if (time_before(jiffies, end)) {
mod_timer(&cfqd->idle_class_timer, end);
cfqq = NULL;
}
}

Expand Down Expand Up @@ -1075,18 +1068,6 @@ static inline int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
return dispatched;
}

static int cfq_forced_dispatch_cfqqs(struct list_head *list)
{
struct cfq_queue *cfqq, *next;
int dispatched;

dispatched = 0;
list_for_each_entry_safe(cfqq, next, list, cfq_list)
dispatched += __cfq_forced_dispatch_cfqq(cfqq);

return dispatched;
}

/*
* Drain our current requests. Used for barriers and when switching
* io schedulers on-the-fly.
Expand All @@ -1102,8 +1083,6 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd)
dispatched += __cfq_forced_dispatch_cfqq(cfqq);
}

dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);

cfq_slice_expired(cfqd, 0, 0);

BUG_ON(cfqd->busy_queues);
Expand Down Expand Up @@ -1433,7 +1412,6 @@ cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
memset(cfqq, 0, sizeof(*cfqq));

INIT_HLIST_NODE(&cfqq->cfq_hash);
INIT_LIST_HEAD(&cfqq->cfq_list);
RB_CLEAR_NODE(&cfqq->rb_node);
INIT_LIST_HEAD(&cfqq->fifo);

Expand Down Expand Up @@ -1712,8 +1690,8 @@ static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
* so we know that it will be selected next.
*/
BUG_ON(!cfq_cfqq_on_rr(cfqq));
list_del_init(&cfqq->cfq_list);
list_add(&cfqq->cfq_list, &cfqd->cur_rr);

cfq_service_tree_add(cfqd, cfqq, 1);

cfqq->slice_end = 0;
cfq_mark_cfqq_slice_new(cfqq);
Expand Down Expand Up @@ -2077,7 +2055,6 @@ static void *cfq_init_queue(request_queue_t *q)
memset(cfqd, 0, sizeof(*cfqd));

cfqd->service_tree = CFQ_RB_ROOT;
INIT_LIST_HEAD(&cfqd->cur_rr);
INIT_LIST_HEAD(&cfqd->cic_list);

cfqd->cfq_hash = kmalloc_node(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL, q->node);
Expand Down

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