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cfq-iosched.c
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/*
* CFQ, or complete fairness queueing, disk scheduler.
*
* Based on ideas from a previously unfinished io
* scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
*
* Copyright (C) 2003 Jens Axboe <axboe@suse.de>
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/blkdev.h>
#include <linux/elevator.h>
#include <linux/hash.h>
#include <linux/rbtree.h>
#include <linux/ioprio.h>
/*
* tunables
*/
static const int cfq_quantum = 4; /* max queue in one round of service */
static const int cfq_queued = 8; /* minimum rq allocate limit per-queue*/
static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
static const int cfq_back_max = 16 * 1024; /* maximum backwards seek, in KiB */
static const int cfq_back_penalty = 2; /* penalty of a backwards seek */
static const int cfq_slice_sync = HZ / 10;
static int cfq_slice_async = HZ / 25;
static const int cfq_slice_async_rq = 2;
static int cfq_slice_idle = HZ / 125;
#define CFQ_IDLE_GRACE (HZ / 10)
#define CFQ_SLICE_SCALE (5)
#define CFQ_KEY_ASYNC (0)
static DEFINE_SPINLOCK(cfq_exit_lock);
/*
* for the hash of cfqq inside the cfqd
*/
#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)
/*
* for the hash of crq inside the cfqq
*/
#define CFQ_MHASH_SHIFT 6
#define CFQ_MHASH_BLOCK(sec) ((sec) >> 3)
#define CFQ_MHASH_ENTRIES (1 << CFQ_MHASH_SHIFT)
#define CFQ_MHASH_FN(sec) hash_long(CFQ_MHASH_BLOCK(sec), CFQ_MHASH_SHIFT)
#define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors)
#define list_entry_hash(ptr) hlist_entry((ptr), struct cfq_rq, hash)
#define list_entry_cfqq(ptr) list_entry((ptr), struct cfq_queue, cfq_list)
#define list_entry_fifo(ptr) list_entry((ptr), struct request, queuelist)
#define RQ_DATA(rq) (rq)->elevator_private
/*
* rb-tree defines
*/
#define rb_entry_crq(node) rb_entry((node), struct cfq_rq, rb_node)
#define rq_rb_key(rq) (rq)->sector
static kmem_cache_t *crq_pool;
static kmem_cache_t *cfq_pool;
static kmem_cache_t *cfq_ioc_pool;
static atomic_t ioc_count = ATOMIC_INIT(0);
static struct completion *ioc_gone;
#define CFQ_PRIO_LISTS IOPRIO_BE_NR
#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
#define cfq_class_be(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_BE)
#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
#define ASYNC (0)
#define SYNC (1)
#define cfq_cfqq_dispatched(cfqq) \
((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC])
#define cfq_cfqq_class_sync(cfqq) ((cfqq)->key != CFQ_KEY_ASYNC)
#define cfq_cfqq_sync(cfqq) \
(cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC])
#define sample_valid(samples) ((samples) > 80)
/*
* Per block device queue structure
*/
struct cfq_data {
request_queue_t *queue;
/*
* 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 int busy_queues;
/*
* non-ordered list of empty cfqq's
*/
struct list_head empty_list;
/*
* cfqq lookup hash
*/
struct hlist_head *cfq_hash;
/*
* global crq hash for all queues
*/
struct hlist_head *crq_hash;
mempool_t *crq_pool;
int rq_in_driver;
int hw_tag;
/*
* schedule slice state info
*/
/*
* idle window management
*/
struct timer_list idle_slice_timer;
struct work_struct unplug_work;
struct cfq_queue *active_queue;
struct cfq_io_context *active_cic;
int cur_prio, cur_end_prio;
unsigned int dispatch_slice;
struct timer_list idle_class_timer;
sector_t last_sector;
unsigned long last_end_request;
unsigned int rq_starved;
/*
* tunables, see top of file
*/
unsigned int cfq_quantum;
unsigned int cfq_queued;
unsigned int cfq_fifo_expire[2];
unsigned int cfq_back_penalty;
unsigned int cfq_back_max;
unsigned int cfq_slice[2];
unsigned int cfq_slice_async_rq;
unsigned int cfq_slice_idle;
struct list_head cic_list;
};
/*
* Per process-grouping structure
*/
struct cfq_queue {
/* reference count */
atomic_t ref;
/* parent cfq_data */
struct cfq_data *cfqd;
/* cfqq lookup hash */
struct hlist_node cfq_hash;
/* hash key */
unsigned int key;
/* on either rr or empty list of cfqd */
struct list_head cfq_list;
/* sorted list of pending requests */
struct rb_root sort_list;
/* if fifo isn't expired, next request to serve */
struct cfq_rq *next_crq;
/* requests queued in sort_list */
int queued[2];
/* currently allocated requests */
int allocated[2];
/* fifo list of requests in sort_list */
struct list_head fifo;
unsigned long slice_start;
unsigned long slice_end;
unsigned long slice_left;
unsigned long service_last;
/* number of requests that are on the dispatch list */
int on_dispatch[2];
/* io prio of this group */
unsigned short ioprio, org_ioprio;
unsigned short ioprio_class, org_ioprio_class;
/* various state flags, see below */
unsigned int flags;
};
struct cfq_rq {
struct rb_node rb_node;
sector_t rb_key;
struct request *request;
struct hlist_node hash;
struct cfq_queue *cfq_queue;
struct cfq_io_context *io_context;
unsigned int crq_flags;
};
enum cfqq_state_flags {
CFQ_CFQQ_FLAG_on_rr = 0,
CFQ_CFQQ_FLAG_wait_request,
CFQ_CFQQ_FLAG_must_alloc,
CFQ_CFQQ_FLAG_must_alloc_slice,
CFQ_CFQQ_FLAG_must_dispatch,
CFQ_CFQQ_FLAG_fifo_expire,
CFQ_CFQQ_FLAG_idle_window,
CFQ_CFQQ_FLAG_prio_changed,
};
#define CFQ_CFQQ_FNS(name) \
static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
{ \
cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
} \
static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
{ \
cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
} \
static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
{ \
return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
}
CFQ_CFQQ_FNS(on_rr);
CFQ_CFQQ_FNS(wait_request);
CFQ_CFQQ_FNS(must_alloc);
CFQ_CFQQ_FNS(must_alloc_slice);
CFQ_CFQQ_FNS(must_dispatch);
CFQ_CFQQ_FNS(fifo_expire);
CFQ_CFQQ_FNS(idle_window);
CFQ_CFQQ_FNS(prio_changed);
#undef CFQ_CFQQ_FNS
enum cfq_rq_state_flags {
CFQ_CRQ_FLAG_is_sync = 0,
};
#define CFQ_CRQ_FNS(name) \
static inline void cfq_mark_crq_##name(struct cfq_rq *crq) \
{ \
crq->crq_flags |= (1 << CFQ_CRQ_FLAG_##name); \
} \
static inline void cfq_clear_crq_##name(struct cfq_rq *crq) \
{ \
crq->crq_flags &= ~(1 << CFQ_CRQ_FLAG_##name); \
} \
static inline int cfq_crq_##name(const struct cfq_rq *crq) \
{ \
return (crq->crq_flags & (1 << CFQ_CRQ_FLAG_##name)) != 0; \
}
CFQ_CRQ_FNS(is_sync);
#undef CFQ_CRQ_FNS
static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *);
static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
/*
* lots of deadline iosched dupes, can be abstracted later...
*/
static inline void cfq_del_crq_hash(struct cfq_rq *crq)
{
hlist_del_init(&crq->hash);
}
static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq)
{
const int hash_idx = CFQ_MHASH_FN(rq_hash_key(crq->request));
hlist_add_head(&crq->hash, &cfqd->crq_hash[hash_idx]);
}
static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset)
{
struct hlist_head *hash_list = &cfqd->crq_hash[CFQ_MHASH_FN(offset)];
struct hlist_node *entry, *next;
hlist_for_each_safe(entry, next, hash_list) {
struct cfq_rq *crq = list_entry_hash(entry);
struct request *__rq = crq->request;
if (!rq_mergeable(__rq)) {
cfq_del_crq_hash(crq);
continue;
}
if (rq_hash_key(__rq) == offset)
return __rq;
}
return NULL;
}
/*
* scheduler run of queue, if there are requests pending and no one in the
* driver that will restart queueing
*/
static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
{
if (cfqd->busy_queues)
kblockd_schedule_work(&cfqd->unplug_work);
}
static int cfq_queue_empty(request_queue_t *q)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
return !cfqd->busy_queues;
}
static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
{
if (rw == READ || rw == WRITE_SYNC)
return task->pid;
return CFQ_KEY_ASYNC;
}
/*
* Lifted from AS - choose which of crq1 and crq2 that is best served now.
* We choose the request that is closest to the head right now. Distance
* behind the head is penalized and only allowed to a certain extent.
*/
static struct cfq_rq *
cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2)
{
sector_t last, s1, s2, d1 = 0, d2 = 0;
unsigned long back_max;
#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
unsigned wrap = 0; /* bit mask: requests behind the disk head? */
if (crq1 == NULL || crq1 == crq2)
return crq2;
if (crq2 == NULL)
return crq1;
if (cfq_crq_is_sync(crq1) && !cfq_crq_is_sync(crq2))
return crq1;
else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1))
return crq2;
s1 = crq1->request->sector;
s2 = crq2->request->sector;
last = cfqd->last_sector;
/*
* by definition, 1KiB is 2 sectors
*/
back_max = cfqd->cfq_back_max * 2;
/*
* Strict one way elevator _except_ in the case where we allow
* short backward seeks which are biased as twice the cost of a
* similar forward seek.
*/
if (s1 >= last)
d1 = s1 - last;
else if (s1 + back_max >= last)
d1 = (last - s1) * cfqd->cfq_back_penalty;
else
wrap |= CFQ_RQ1_WRAP;
if (s2 >= last)
d2 = s2 - last;
else if (s2 + back_max >= last)
d2 = (last - s2) * cfqd->cfq_back_penalty;
else
wrap |= CFQ_RQ2_WRAP;
/* Found required data */
/*
* By doing switch() on the bit mask "wrap" we avoid having to
* check two variables for all permutations: --> faster!
*/
switch (wrap) {
case 0: /* common case for CFQ: crq1 and crq2 not wrapped */
if (d1 < d2)
return crq1;
else if (d2 < d1)
return crq2;
else {
if (s1 >= s2)
return crq1;
else
return crq2;
}
case CFQ_RQ2_WRAP:
return crq1;
case CFQ_RQ1_WRAP:
return crq2;
case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both crqs wrapped */
default:
/*
* Since both rqs are wrapped,
* start with the one that's further behind head
* (--> only *one* back seek required),
* since back seek takes more time than forward.
*/
if (s1 <= s2)
return crq1;
else
return crq2;
}
}
/*
* would be nice to take fifo expire time into account as well
*/
static struct cfq_rq *
cfq_find_next_crq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct cfq_rq *last)
{
struct cfq_rq *crq_next = NULL, *crq_prev = NULL;
struct rb_node *rbnext, *rbprev;
if (!(rbnext = rb_next(&last->rb_node))) {
rbnext = rb_first(&cfqq->sort_list);
if (rbnext == &last->rb_node)
rbnext = NULL;
}
rbprev = rb_prev(&last->rb_node);
if (rbprev)
crq_prev = rb_entry_crq(rbprev);
if (rbnext)
crq_next = rb_entry_crq(rbnext);
return cfq_choose_req(cfqd, crq_next, crq_prev);
}
static void cfq_update_next_crq(struct cfq_rq *crq)
{
struct cfq_queue *cfqq = crq->cfq_queue;
if (cfqq->next_crq == crq)
cfqq->next_crq = cfq_find_next_crq(cfqq->cfqd, cfqq, crq);
}
static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
{
struct cfq_data *cfqd = cfqq->cfqd;
struct list_head *list, *entry;
BUG_ON(!cfq_cfqq_on_rr(cfqq));
list_del(&cfqq->cfq_list);
if (cfq_class_rt(cfqq))
list = &cfqd->cur_rr;
else if (cfq_class_idle(cfqq))
list = &cfqd->idle_rr;
else {
/*
* 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 (cfq_cfqq_dispatched(cfqq))
list = &cfqd->busy_rr;
else
list = &cfqd->rr_list[cfqq->ioprio];
}
/*
* if queue was preempted, just add to front to be fair. busy_rr
* isn't sorted, but insert at the back for fairness.
*/
if (preempted || list == &cfqd->busy_rr) {
if (preempted)
list = list->prev;
list_add_tail(&cfqq->cfq_list, list);
return;
}
/*
* sort by when queue was last serviced
*/
entry = list;
while ((entry = entry->prev) != list) {
struct cfq_queue *__cfqq = list_entry_cfqq(entry);
if (!__cfqq->service_last)
break;
if (time_before(__cfqq->service_last, cfqq->service_last))
break;
}
list_add(&cfqq->cfq_list, entry);
}
/*
* add to busy list of queues for service, trying to be fair in ordering
* the pending list according to last request service
*/
static inline void
cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
BUG_ON(cfq_cfqq_on_rr(cfqq));
cfq_mark_cfqq_on_rr(cfqq);
cfqd->busy_queues++;
cfq_resort_rr_list(cfqq, 0);
}
static inline void
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_move(&cfqq->cfq_list, &cfqd->empty_list);
BUG_ON(!cfqd->busy_queues);
cfqd->busy_queues--;
}
/*
* rb tree support functions
*/
static inline void cfq_del_crq_rb(struct cfq_rq *crq)
{
struct cfq_queue *cfqq = crq->cfq_queue;
struct cfq_data *cfqd = cfqq->cfqd;
const int sync = cfq_crq_is_sync(crq);
BUG_ON(!cfqq->queued[sync]);
cfqq->queued[sync]--;
cfq_update_next_crq(crq);
rb_erase(&crq->rb_node, &cfqq->sort_list);
if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
cfq_del_cfqq_rr(cfqd, cfqq);
}
static struct cfq_rq *
__cfq_add_crq_rb(struct cfq_rq *crq)
{
struct rb_node **p = &crq->cfq_queue->sort_list.rb_node;
struct rb_node *parent = NULL;
struct cfq_rq *__crq;
while (*p) {
parent = *p;
__crq = rb_entry_crq(parent);
if (crq->rb_key < __crq->rb_key)
p = &(*p)->rb_left;
else if (crq->rb_key > __crq->rb_key)
p = &(*p)->rb_right;
else
return __crq;
}
rb_link_node(&crq->rb_node, parent, p);
return NULL;
}
static void cfq_add_crq_rb(struct cfq_rq *crq)
{
struct cfq_queue *cfqq = crq->cfq_queue;
struct cfq_data *cfqd = cfqq->cfqd;
struct request *rq = crq->request;
struct cfq_rq *__alias;
crq->rb_key = rq_rb_key(rq);
cfqq->queued[cfq_crq_is_sync(crq)]++;
/*
* looks a little odd, but the first insert might return an alias.
* if that happens, put the alias on the dispatch list
*/
while ((__alias = __cfq_add_crq_rb(crq)) != NULL)
cfq_dispatch_insert(cfqd->queue, __alias);
rb_insert_color(&crq->rb_node, &cfqq->sort_list);
if (!cfq_cfqq_on_rr(cfqq))
cfq_add_cfqq_rr(cfqd, cfqq);
/*
* check if this request is a better next-serve candidate
*/
cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
}
static inline void
cfq_reposition_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq)
{
rb_erase(&crq->rb_node, &cfqq->sort_list);
cfqq->queued[cfq_crq_is_sync(crq)]--;
cfq_add_crq_rb(crq);
}
static struct request *
cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
{
struct task_struct *tsk = current;
pid_t key = cfq_queue_pid(tsk, bio_data_dir(bio));
struct cfq_queue *cfqq;
struct rb_node *n;
sector_t sector;
cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
if (!cfqq)
goto out;
sector = bio->bi_sector + bio_sectors(bio);
n = cfqq->sort_list.rb_node;
while (n) {
struct cfq_rq *crq = rb_entry_crq(n);
if (sector < crq->rb_key)
n = n->rb_left;
else if (sector > crq->rb_key)
n = n->rb_right;
else
return crq->request;
}
out:
return NULL;
}
static void cfq_activate_request(request_queue_t *q, struct request *rq)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
cfqd->rq_in_driver++;
/*
* If the depth is larger 1, it really could be queueing. But lets
* make the mark a little higher - idling could still be good for
* low queueing, and a low queueing number could also just indicate
* a SCSI mid layer like behaviour where limit+1 is often seen.
*/
if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
cfqd->hw_tag = 1;
}
static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
WARN_ON(!cfqd->rq_in_driver);
cfqd->rq_in_driver--;
}
static void cfq_remove_request(struct request *rq)
{
struct cfq_rq *crq = RQ_DATA(rq);
list_del_init(&rq->queuelist);
cfq_del_crq_rb(crq);
cfq_del_crq_hash(crq);
}
static int
cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct request *__rq;
int ret;
__rq = cfq_find_rq_hash(cfqd, bio->bi_sector);
if (__rq && elv_rq_merge_ok(__rq, bio)) {
ret = ELEVATOR_BACK_MERGE;
goto out;
}
__rq = cfq_find_rq_fmerge(cfqd, bio);
if (__rq && elv_rq_merge_ok(__rq, bio)) {
ret = ELEVATOR_FRONT_MERGE;
goto out;
}
return ELEVATOR_NO_MERGE;
out:
*req = __rq;
return ret;
}
static void cfq_merged_request(request_queue_t *q, struct request *req)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_rq *crq = RQ_DATA(req);
cfq_del_crq_hash(crq);
cfq_add_crq_hash(cfqd, crq);
if (rq_rb_key(req) != crq->rb_key) {
struct cfq_queue *cfqq = crq->cfq_queue;
cfq_update_next_crq(crq);
cfq_reposition_crq_rb(cfqq, crq);
}
}
static void
cfq_merged_requests(request_queue_t *q, struct request *rq,
struct request *next)
{
cfq_merged_request(q, rq);
/*
* reposition in fifo if next is older than rq
*/
if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
time_before(next->start_time, rq->start_time))
list_move(&rq->queuelist, &next->queuelist);
cfq_remove_request(next);
}
static inline void
__cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
if (cfqq) {
/*
* stop potential idle class queues waiting service
*/
del_timer(&cfqd->idle_class_timer);
cfqq->slice_start = jiffies;
cfqq->slice_end = 0;
cfqq->slice_left = 0;
cfq_clear_cfqq_must_alloc_slice(cfqq);
cfq_clear_cfqq_fifo_expire(cfqq);
}
cfqd->active_queue = cfqq;
}
/*
* current cfqq expired its slice (or was too idle), select new one
*/
static void
__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
int preempted)
{
unsigned long now = jiffies;
if (cfq_cfqq_wait_request(cfqq))
del_timer(&cfqd->idle_slice_timer);
if (!preempted && !cfq_cfqq_dispatched(cfqq)) {
cfqq->service_last = now;
cfq_schedule_dispatch(cfqd);
}
cfq_clear_cfqq_must_dispatch(cfqq);
cfq_clear_cfqq_wait_request(cfqq);
/*
* store what was left of this slice, if the queue idled out
* or was preempted
*/
if (time_after(cfqq->slice_end, now))
cfqq->slice_left = cfqq->slice_end - now;
else
cfqq->slice_left = 0;
if (cfq_cfqq_on_rr(cfqq))
cfq_resort_rr_list(cfqq, preempted);
if (cfqq == cfqd->active_queue)
cfqd->active_queue = NULL;
if (cfqd->active_cic) {
put_io_context(cfqd->active_cic->ioc);
cfqd->active_cic = NULL;
}
cfqd->dispatch_slice = 0;
}
static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted)
{
struct cfq_queue *cfqq = cfqd->active_queue;
if (cfqq)
__cfq_slice_expired(cfqd, cfqq, preempted);
}
/*
* 0
* 0,1
* 0,1,2
* 0,1,2,3
* 0,1,2,3,4
* 0,1,2,3,4,5
* 0,1,2,3,4,5,6
* 0,1,2,3,4,5,6,7
*/
static int cfq_get_next_prio_level(struct cfq_data *cfqd)
{
int prio, wrap;
prio = -1;
wrap = 0;
do {
int p;
for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
if (!list_empty(&cfqd->rr_list[p])) {
prio = p;
break;
}
}
if (prio != -1)
break;
cfqd->cur_prio = 0;
if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
cfqd->cur_end_prio = 0;
if (wrap)
break;
wrap = 1;
}
} while (1);
if (unlikely(prio == -1))
return -1;
BUG_ON(prio >= CFQ_PRIO_LISTS);
list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
cfqd->cur_prio = prio + 1;
if (cfqd->cur_prio > cfqd->cur_end_prio) {
cfqd->cur_end_prio = cfqd->cur_prio;
cfqd->cur_prio = 0;
}
if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
cfqd->cur_prio = 0;
cfqd->cur_end_prio = 0;
}
return prio;
}
static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq = NULL;
/*
* if current list is non-empty, grab first entry. if it is empty,
* get next prio level and grab first entry then if any are spliced
*/
if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1)
cfqq = list_entry_cfqq(cfqd->cur_rr.next);
/*
* If no new queues are available, check if the busy list has some
* before falling back to idle io.
*/
if (!cfqq && !list_empty(&cfqd->busy_rr))
cfqq = list_entry_cfqq(cfqd->busy_rr.next);
/*
* 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
*/
if (!cfqq && !list_empty(&cfqd->idle_rr)) {
unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
if (time_after_eq(jiffies, end))
cfqq = list_entry_cfqq(cfqd->idle_rr.next);
else
mod_timer(&cfqd->idle_class_timer, end);
}
__cfq_set_active_queue(cfqd, cfqq);
return cfqq;
}
#define CIC_SEEKY(cic) ((cic)->seek_mean > (128 * 1024))
static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
struct cfq_io_context *cic;
unsigned long sl;
WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
WARN_ON(cfqq != cfqd->active_queue);
/*
* idle is disabled, either manually or by past process history
*/
if (!cfqd->cfq_slice_idle)
return 0;
if (!cfq_cfqq_idle_window(cfqq))
return 0;
/*
* task has exited, don't wait
*/
cic = cfqd->active_cic;
if (!cic || !cic->ioc->task)
return 0;
cfq_mark_cfqq_must_dispatch(cfqq);
cfq_mark_cfqq_wait_request(cfqq);
sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle);
/*
* we don't want to idle for seeks, but we do want to allow
* fair distribution of slice time for a process doing back-to-back
* seeks. so allow a little bit of time for him to submit a new rq
*/
if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
sl = 2;
mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
return 1;
}
static void cfq_dispatch_insert(request_queue_t *q, struct cfq_rq *crq)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_queue *cfqq = crq->cfq_queue;
struct request *rq;
cfqq->next_crq = cfq_find_next_crq(cfqd, cfqq, crq);
cfq_remove_request(crq->request);
cfqq->on_dispatch[cfq_crq_is_sync(crq)]++;
elv_dispatch_sort(q, crq->request);
rq = list_entry(q->queue_head.prev, struct request, queuelist);
cfqd->last_sector = rq->sector + rq->nr_sectors;
}
/*
* return expired entry, or NULL to just start from scratch in rbtree
*/
static inline struct cfq_rq *cfq_check_fifo(struct cfq_queue *cfqq)
{
struct cfq_data *cfqd = cfqq->cfqd;
struct request *rq;
struct cfq_rq *crq;
if (cfq_cfqq_fifo_expire(cfqq))
return NULL;
if (!list_empty(&cfqq->fifo)) {
int fifo = cfq_cfqq_class_sync(cfqq);
crq = RQ_DATA(list_entry_fifo(cfqq->fifo.next));
rq = crq->request;
if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) {
cfq_mark_cfqq_fifo_expire(cfqq);
return crq;
}
}
return NULL;
}
/*
* Scale schedule slice based on io priority. Use the sync time slice only
* if a queue is marked sync and has sync io queued. A sync queue with async
* io only, should not get full sync slice length.
*/
static inline int
cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)];
WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio));
}