linux/block/cfq-iosched.c
Jens Axboe 5fccbf61be [PATCH] CFQ: request <-> request merging rr_list fixup
In very rare circumstances would we be pruning a merged request and at
the same time delete the implicated cfqq from the rr_list, and not readd
it when the merged request got added. This could cause io stalls until
that process issued io again.

Fix it up by putting the rr_list add handling into cfq_add_rq_rb(),
identical to how pruning is handled in cfq_del_rq_rb(). This fixes a
hang reproducible with fsx-linux.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-31 08:12:45 -08:00

2182 lines
51 KiB
C

/*
* 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@kernel.dk>
*/
#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_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)
/*
* 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)
#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)
static kmem_cache_t *cfq_pool;
static kmem_cache_t *cfq_ioc_pool;
static DEFINE_PER_CPU(unsigned long, ioc_count);
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_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;
/*
* cfqq lookup hash
*/
struct hlist_head *cfq_hash;
int rq_in_driver;
int hw_tag;
/*
* 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;
/*
* tunables, see top of file
*/
unsigned int cfq_quantum;
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;
/* member of the rr/busy/cur/idle cfqd list */
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 request *next_rq;
/* requests queued in sort_list */
int queued[2];
/* currently allocated requests */
int allocated[2];
/* pending metadata requests */
int meta_pending;
/* fifo list of requests in sort_list */
struct list_head fifo;
unsigned long slice_start;
unsigned long slice_end;
unsigned long slice_left;
/* 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;
};
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,
CFQ_CFQQ_FLAG_queue_new,
};
#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);
CFQ_CFQQ_FNS(queue_new);
#undef CFQ_CFQQ_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 request *);
static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
/*
* 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 rq1 and rq2 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 request *
cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
{
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 (rq1 == NULL || rq1 == rq2)
return rq2;
if (rq2 == NULL)
return rq1;
if (rq_is_sync(rq1) && !rq_is_sync(rq2))
return rq1;
else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
return rq2;
if (rq_is_meta(rq1) && !rq_is_meta(rq2))
return rq1;
else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
return rq2;
s1 = rq1->sector;
s2 = rq2->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: rq1 and rq2 not wrapped */
if (d1 < d2)
return rq1;
else if (d2 < d1)
return rq2;
else {
if (s1 >= s2)
return rq1;
else
return rq2;
}
case CFQ_RQ2_WRAP:
return rq1;
case CFQ_RQ1_WRAP:
return rq2;
case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs 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 rq1;
else
return rq2;
}
}
/*
* would be nice to take fifo expire time into account as well
*/
static struct request *
cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct request *last)
{
struct rb_node *rbnext = rb_next(&last->rb_node);
struct rb_node *rbprev = rb_prev(&last->rb_node);
struct request *next = NULL, *prev = NULL;
BUG_ON(RB_EMPTY_NODE(&last->rb_node));
if (rbprev)
prev = rb_entry_rq(rbprev);
if (rbnext)
next = rb_entry_rq(rbnext);
else {
rbnext = rb_first(&cfqq->sort_list);
if (rbnext && rbnext != &last->rb_node)
next = rb_entry_rq(rbnext);
}
return cfq_choose_req(cfqd, next, prev);
}
static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
{
struct cfq_data *cfqd = cfqq->cfqd;
struct list_head *list;
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 this queue was preempted or is new (never been serviced), let
* it be added first for fairness but beind other new queues.
* Otherwise, just add to the back of the list.
*/
if (preempted || cfq_cfqq_queue_new(cfqq)) {
struct list_head *n = list;
struct cfq_queue *__cfqq;
while (n->next != list) {
__cfqq = list_entry_cfqq(n->next);
if (!cfq_cfqq_queue_new(__cfqq))
break;
n = n->next;
}
list = n;
}
list_add_tail(&cfqq->cfq_list, list);
}
/*
* 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_del_init(&cfqq->cfq_list);
BUG_ON(!cfqd->busy_queues);
cfqd->busy_queues--;
}
/*
* rb tree support functions
*/
static inline void cfq_del_rq_rb(struct request *rq)
{
struct cfq_queue *cfqq = RQ_CFQQ(rq);
struct cfq_data *cfqd = cfqq->cfqd;
const int sync = rq_is_sync(rq);
BUG_ON(!cfqq->queued[sync]);
cfqq->queued[sync]--;
elv_rb_del(&cfqq->sort_list, rq);
if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
cfq_del_cfqq_rr(cfqd, cfqq);
}
static void cfq_add_rq_rb(struct request *rq)
{
struct cfq_queue *cfqq = RQ_CFQQ(rq);
struct cfq_data *cfqd = cfqq->cfqd;
struct request *__alias;
cfqq->queued[rq_is_sync(rq)]++;
/*
* looks a little odd, but the first insert might return an alias.
* if that happens, put the alias on the dispatch list
*/
while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
cfq_dispatch_insert(cfqd->queue, __alias);
if (!cfq_cfqq_on_rr(cfqq))
cfq_add_cfqq_rr(cfqd, cfqq);
}
static inline void
cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
{
elv_rb_del(&cfqq->sort_list, rq);
cfqq->queued[rq_is_sync(rq)]--;
cfq_add_rq_rb(rq);
}
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;
cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
if (cfqq) {
sector_t sector = bio->bi_sector + bio_sectors(bio);
return elv_rb_find(&cfqq->sort_list, sector);
}
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_queue *cfqq = RQ_CFQQ(rq);
if (cfqq->next_rq == rq)
cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
list_del_init(&rq->queuelist);
cfq_del_rq_rb(rq);
if (rq_is_meta(rq)) {
WARN_ON(!cfqq->meta_pending);
cfqq->meta_pending--;
}
}
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;
__rq = cfq_find_rq_fmerge(cfqd, bio);
if (__rq && elv_rq_merge_ok(__rq, bio)) {
*req = __rq;
return ELEVATOR_FRONT_MERGE;
}
return ELEVATOR_NO_MERGE;
}
static void cfq_merged_request(request_queue_t *q, struct request *req,
int type)
{
if (type == ELEVATOR_FRONT_MERGE) {
struct cfq_queue *cfqq = RQ_CFQQ(req);
cfq_reposition_rq_rb(cfqq, req);
}
}
static void
cfq_merged_requests(request_queue_t *q, struct request *rq,
struct request *next)
{
/*
* 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))
cfq_schedule_dispatch(cfqd);
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
* 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 (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1) {
/*
* 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
*/
cfqq = list_entry_cfqq(cfqd->cur_rr.next);
} 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
* requests, either allow immediate service if the grace period
* has passed or arm the idle grace timer
*/
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 = min(sl, msecs_to_jiffies(2));
mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
return 1;
}
static void cfq_dispatch_insert(request_queue_t *q, struct request *rq)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_queue *cfqq = RQ_CFQQ(rq);
cfq_remove_request(rq);
cfqq->on_dispatch[rq_is_sync(rq)]++;
elv_dispatch_sort(q, rq);
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 request *cfq_check_fifo(struct cfq_queue *cfqq)
{
struct cfq_data *cfqd = cfqq->cfqd;
struct request *rq;
int fifo;
if (cfq_cfqq_fifo_expire(cfqq))
return NULL;
if (list_empty(&cfqq->fifo))
return NULL;
fifo = cfq_cfqq_class_sync(cfqq);
rq = rq_entry_fifo(cfqq->fifo.next);
if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) {
cfq_mark_cfqq_fifo_expire(cfqq);
return rq;
}
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));
}
static inline void
cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
}
static inline int
cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
const int base_rq = cfqd->cfq_slice_async_rq;
WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
}
/*
* get next queue for service
*/
static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
{
unsigned long now = jiffies;
struct cfq_queue *cfqq;
cfqq = cfqd->active_queue;
if (!cfqq)
goto new_queue;
/*
* slice has expired
*/
if (!cfq_cfqq_must_dispatch(cfqq) && time_after(now, cfqq->slice_end))
goto expire;
/*
* if queue has requests, dispatch one. if not, check if
* enough slice is left to wait for one
*/
if (!RB_EMPTY_ROOT(&cfqq->sort_list))
goto keep_queue;
else if (cfq_cfqq_dispatched(cfqq)) {
cfqq = NULL;
goto keep_queue;
} else if (cfq_cfqq_class_sync(cfqq)) {
if (cfq_arm_slice_timer(cfqd, cfqq))
return NULL;
}
expire:
cfq_slice_expired(cfqd, 0);
new_queue:
cfqq = cfq_set_active_queue(cfqd);
keep_queue:
return cfqq;
}
static int
__cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
int max_dispatch)
{
int dispatched = 0;
BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
do {
struct request *rq;
/*
* follow expired path, else get first next available
*/
if ((rq = cfq_check_fifo(cfqq)) == NULL)
rq = cfqq->next_rq;
/*
* finally, insert request into driver dispatch list
*/
cfq_dispatch_insert(cfqd->queue, rq);
cfqd->dispatch_slice++;
dispatched++;
if (!cfqd->active_cic) {
atomic_inc(&RQ_CIC(rq)->ioc->refcount);
cfqd->active_cic = RQ_CIC(rq);
}
if (RB_EMPTY_ROOT(&cfqq->sort_list))
break;
} while (dispatched < max_dispatch);
/*
* if slice end isn't set yet, set it.
*/
if (!cfqq->slice_end)
cfq_set_prio_slice(cfqd, cfqq);
/*
* expire an async queue immediately if it has used up its slice. idle
* queue always expire after 1 dispatch round.
*/
if ((!cfq_cfqq_sync(cfqq) &&
cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
cfq_class_idle(cfqq) ||
!cfq_cfqq_idle_window(cfqq))
cfq_slice_expired(cfqd, 0);
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) {
while (cfqq->next_rq) {
cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
dispatched++;
}
BUG_ON(!list_empty(&cfqq->fifo));
}
return dispatched;
}
static int
cfq_forced_dispatch(struct cfq_data *cfqd)
{
int i, dispatched = 0;
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);
cfq_slice_expired(cfqd, 0);
BUG_ON(cfqd->busy_queues);
return dispatched;
}
static int
cfq_dispatch_requests(request_queue_t *q, int force)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_queue *cfqq, *prev_cfqq;
int dispatched;
if (!cfqd->busy_queues)
return 0;
if (unlikely(force))
return cfq_forced_dispatch(cfqd);
dispatched = 0;
prev_cfqq = NULL;
while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
int max_dispatch;
/*
* Don't repeat dispatch from the previous queue.
*/
if (prev_cfqq == cfqq)
break;
cfq_clear_cfqq_must_dispatch(cfqq);
cfq_clear_cfqq_wait_request(cfqq);
del_timer(&cfqd->idle_slice_timer);
max_dispatch = cfqd->cfq_quantum;
if (cfq_class_idle(cfqq))
max_dispatch = 1;
dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
/*
* If the dispatch cfqq has idling enabled and is still
* the active queue, break out.
*/
if (cfq_cfqq_idle_window(cfqq) && cfqd->active_queue)
break;
prev_cfqq = cfqq;
}
return dispatched;
}
/*
* task holds one reference to the queue, dropped when task exits. each rq
* in-flight on this queue also holds a reference, dropped when rq is freed.
*
* queue lock must be held here.
*/
static void cfq_put_queue(struct cfq_queue *cfqq)
{
struct cfq_data *cfqd = cfqq->cfqd;
BUG_ON(atomic_read(&cfqq->ref) <= 0);
if (!atomic_dec_and_test(&cfqq->ref))
return;
BUG_ON(rb_first(&cfqq->sort_list));
BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
BUG_ON(cfq_cfqq_on_rr(cfqq));
if (unlikely(cfqd->active_queue == cfqq))
__cfq_slice_expired(cfqd, cfqq, 0);
/*
* it's on the empty list and still hashed
*/
list_del(&cfqq->cfq_list);
hlist_del(&cfqq->cfq_hash);
kmem_cache_free(cfq_pool, cfqq);
}
static struct cfq_queue *
__cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
const int hashval)
{
struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
struct hlist_node *entry;
struct cfq_queue *__cfqq;
hlist_for_each_entry(__cfqq, entry, hash_list, cfq_hash) {
const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio);
if (__cfqq->key == key && (__p == prio || !prio))
return __cfqq;
}
return NULL;
}
static struct cfq_queue *
cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
{
return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
}
static void cfq_free_io_context(struct io_context *ioc)
{
struct cfq_io_context *__cic;
struct rb_node *n;
int freed = 0;
while ((n = rb_first(&ioc->cic_root)) != NULL) {
__cic = rb_entry(n, struct cfq_io_context, rb_node);
rb_erase(&__cic->rb_node, &ioc->cic_root);
kmem_cache_free(cfq_ioc_pool, __cic);
freed++;
}
elv_ioc_count_mod(ioc_count, -freed);
if (ioc_gone && !elv_ioc_count_read(ioc_count))
complete(ioc_gone);
}
static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
if (unlikely(cfqq == cfqd->active_queue))
__cfq_slice_expired(cfqd, cfqq, 0);
cfq_put_queue(cfqq);
}
static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
struct cfq_io_context *cic)
{
list_del_init(&cic->queue_list);
smp_wmb();
cic->key = NULL;
if (cic->cfqq[ASYNC]) {
cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);
cic->cfqq[ASYNC] = NULL;
}
if (cic->cfqq[SYNC]) {
cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]);
cic->cfqq[SYNC] = NULL;
}
}
/*
* Called with interrupts disabled
*/
static void cfq_exit_single_io_context(struct cfq_io_context *cic)
{
struct cfq_data *cfqd = cic->key;
if (cfqd) {
request_queue_t *q = cfqd->queue;
spin_lock_irq(q->queue_lock);
__cfq_exit_single_io_context(cfqd, cic);
spin_unlock_irq(q->queue_lock);
}
}
static void cfq_exit_io_context(struct io_context *ioc)
{
struct cfq_io_context *__cic;
struct rb_node *n;
/*
* put the reference this task is holding to the various queues
*/
n = rb_first(&ioc->cic_root);
while (n != NULL) {
__cic = rb_entry(n, struct cfq_io_context, rb_node);
cfq_exit_single_io_context(__cic);
n = rb_next(n);
}
}
static struct cfq_io_context *
cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
{
struct cfq_io_context *cic;
cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask, cfqd->queue->node);
if (cic) {
memset(cic, 0, sizeof(*cic));
cic->last_end_request = jiffies;
INIT_LIST_HEAD(&cic->queue_list);
cic->dtor = cfq_free_io_context;
cic->exit = cfq_exit_io_context;
elv_ioc_count_inc(ioc_count);
}
return cic;
}
static void cfq_init_prio_data(struct cfq_queue *cfqq)
{
struct task_struct *tsk = current;
int ioprio_class;
if (!cfq_cfqq_prio_changed(cfqq))
return;
ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
switch (ioprio_class) {
default:
printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
case IOPRIO_CLASS_NONE:
/*
* no prio set, place us in the middle of the BE classes
*/
cfqq->ioprio = task_nice_ioprio(tsk);
cfqq->ioprio_class = IOPRIO_CLASS_BE;
break;
case IOPRIO_CLASS_RT:
cfqq->ioprio = task_ioprio(tsk);
cfqq->ioprio_class = IOPRIO_CLASS_RT;
break;
case IOPRIO_CLASS_BE:
cfqq->ioprio = task_ioprio(tsk);
cfqq->ioprio_class = IOPRIO_CLASS_BE;
break;
case IOPRIO_CLASS_IDLE:
cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
cfqq->ioprio = 7;
cfq_clear_cfqq_idle_window(cfqq);
break;
}
/*
* keep track of original prio settings in case we have to temporarily
* elevate the priority of this queue
*/
cfqq->org_ioprio = cfqq->ioprio;
cfqq->org_ioprio_class = cfqq->ioprio_class;
if (cfq_cfqq_on_rr(cfqq))
cfq_resort_rr_list(cfqq, 0);
cfq_clear_cfqq_prio_changed(cfqq);
}
static inline void changed_ioprio(struct cfq_io_context *cic)
{
struct cfq_data *cfqd = cic->key;
struct cfq_queue *cfqq;
unsigned long flags;
if (unlikely(!cfqd))
return;
spin_lock_irqsave(cfqd->queue->queue_lock, flags);
cfqq = cic->cfqq[ASYNC];
if (cfqq) {
struct cfq_queue *new_cfqq;
new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC, cic->ioc->task,
GFP_ATOMIC);
if (new_cfqq) {
cic->cfqq[ASYNC] = new_cfqq;
cfq_put_queue(cfqq);
}
}
cfqq = cic->cfqq[SYNC];
if (cfqq)
cfq_mark_cfqq_prio_changed(cfqq);
spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}
static void cfq_ioc_set_ioprio(struct io_context *ioc)
{
struct cfq_io_context *cic;
struct rb_node *n;
ioc->ioprio_changed = 0;
n = rb_first(&ioc->cic_root);
while (n != NULL) {
cic = rb_entry(n, struct cfq_io_context, rb_node);
changed_ioprio(cic);
n = rb_next(n);
}
}
static struct cfq_queue *
cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
gfp_t gfp_mask)
{
const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
struct cfq_queue *cfqq, *new_cfqq = NULL;
unsigned short ioprio;
retry:
ioprio = tsk->ioprio;
cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
if (!cfqq) {
if (new_cfqq) {
cfqq = new_cfqq;
new_cfqq = NULL;
} else if (gfp_mask & __GFP_WAIT) {
/*
* Inform the allocator of the fact that we will
* just repeat this allocation if it fails, to allow
* the allocator to do whatever it needs to attempt to
* free memory.
*/
spin_unlock_irq(cfqd->queue->queue_lock);
new_cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask|__GFP_NOFAIL, cfqd->queue->node);
spin_lock_irq(cfqd->queue->queue_lock);
goto retry;
} else {
cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask, cfqd->queue->node);
if (!cfqq)
goto out;
}
memset(cfqq, 0, sizeof(*cfqq));
INIT_HLIST_NODE(&cfqq->cfq_hash);
INIT_LIST_HEAD(&cfqq->cfq_list);
INIT_LIST_HEAD(&cfqq->fifo);
cfqq->key = key;
hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
atomic_set(&cfqq->ref, 0);
cfqq->cfqd = cfqd;
/*
* set ->slice_left to allow preemption for a new process
*/
cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
cfq_mark_cfqq_idle_window(cfqq);
cfq_mark_cfqq_prio_changed(cfqq);
cfq_mark_cfqq_queue_new(cfqq);
cfq_init_prio_data(cfqq);
}
if (new_cfqq)
kmem_cache_free(cfq_pool, new_cfqq);
atomic_inc(&cfqq->ref);
out:
WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
return cfqq;
}
static void
cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
{
WARN_ON(!list_empty(&cic->queue_list));
rb_erase(&cic->rb_node, &ioc->cic_root);
kmem_cache_free(cfq_ioc_pool, cic);
elv_ioc_count_dec(ioc_count);
}
static struct cfq_io_context *
cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
{
struct rb_node *n;
struct cfq_io_context *cic;
void *k, *key = cfqd;
restart:
n = ioc->cic_root.rb_node;
while (n) {
cic = rb_entry(n, struct cfq_io_context, rb_node);
/* ->key must be copied to avoid race with cfq_exit_queue() */
k = cic->key;
if (unlikely(!k)) {
cfq_drop_dead_cic(ioc, cic);
goto restart;
}
if (key < k)
n = n->rb_left;
else if (key > k)
n = n->rb_right;
else
return cic;
}
return NULL;
}
static inline void
cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
struct cfq_io_context *cic)
{
struct rb_node **p;
struct rb_node *parent;
struct cfq_io_context *__cic;
unsigned long flags;
void *k;
cic->ioc = ioc;
cic->key = cfqd;
restart:
parent = NULL;
p = &ioc->cic_root.rb_node;
while (*p) {
parent = *p;
__cic = rb_entry(parent, struct cfq_io_context, rb_node);
/* ->key must be copied to avoid race with cfq_exit_queue() */
k = __cic->key;
if (unlikely(!k)) {
cfq_drop_dead_cic(ioc, __cic);
goto restart;
}
if (cic->key < k)
p = &(*p)->rb_left;
else if (cic->key > k)
p = &(*p)->rb_right;
else
BUG();
}
rb_link_node(&cic->rb_node, parent, p);
rb_insert_color(&cic->rb_node, &ioc->cic_root);
spin_lock_irqsave(cfqd->queue->queue_lock, flags);
list_add(&cic->queue_list, &cfqd->cic_list);
spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}
/*
* Setup general io context and cfq io context. There can be several cfq
* io contexts per general io context, if this process is doing io to more
* than one device managed by cfq.
*/
static struct cfq_io_context *
cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
{
struct io_context *ioc = NULL;
struct cfq_io_context *cic;
might_sleep_if(gfp_mask & __GFP_WAIT);
ioc = get_io_context(gfp_mask, cfqd->queue->node);
if (!ioc)
return NULL;
cic = cfq_cic_rb_lookup(cfqd, ioc);
if (cic)
goto out;
cic = cfq_alloc_io_context(cfqd, gfp_mask);
if (cic == NULL)
goto err;
cfq_cic_link(cfqd, ioc, cic);
out:
smp_read_barrier_depends();
if (unlikely(ioc->ioprio_changed))
cfq_ioc_set_ioprio(ioc);
return cic;
err:
put_io_context(ioc);
return NULL;
}
static void
cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
{
unsigned long elapsed, ttime;
/*
* if this context already has stuff queued, thinktime is from
* last queue not last end
*/
#if 0
if (time_after(cic->last_end_request, cic->last_queue))
elapsed = jiffies - cic->last_end_request;
else
elapsed = jiffies - cic->last_queue;
#else
elapsed = jiffies - cic->last_end_request;
#endif
ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
}
static void
cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
struct request *rq)
{
sector_t sdist;
u64 total;
if (cic->last_request_pos < rq->sector)
sdist = rq->sector - cic->last_request_pos;
else
sdist = cic->last_request_pos - rq->sector;
/*
* Don't allow the seek distance to get too large from the
* odd fragment, pagein, etc
*/
if (cic->seek_samples <= 60) /* second&third seek */
sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
else
sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
cic->seek_samples = (7*cic->seek_samples + 256) / 8;
cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
total = cic->seek_total + (cic->seek_samples/2);
do_div(total, cic->seek_samples);
cic->seek_mean = (sector_t)total;
}
/*
* Disable idle window if the process thinks too long or seeks so much that
* it doesn't matter
*/
static void
cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct cfq_io_context *cic)
{
int enable_idle = cfq_cfqq_idle_window(cfqq);
if (!cic->ioc->task || !cfqd->cfq_slice_idle ||
(cfqd->hw_tag && CIC_SEEKY(cic)))
enable_idle = 0;
else if (sample_valid(cic->ttime_samples)) {
if (cic->ttime_mean > cfqd->cfq_slice_idle)
enable_idle = 0;
else
enable_idle = 1;
}
if (enable_idle)
cfq_mark_cfqq_idle_window(cfqq);
else
cfq_clear_cfqq_idle_window(cfqq);
}
/*
* Check if new_cfqq should preempt the currently active queue. Return 0 for
* no or if we aren't sure, a 1 will cause a preempt.
*/
static int
cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
struct request *rq)
{
struct cfq_queue *cfqq = cfqd->active_queue;
if (cfq_class_idle(new_cfqq))
return 0;
if (!cfqq)
return 0;
if (cfq_class_idle(cfqq))
return 1;
if (!cfq_cfqq_wait_request(new_cfqq))
return 0;
/*
* if it doesn't have slice left, forget it
*/
if (new_cfqq->slice_left < cfqd->cfq_slice_idle)
return 0;
/*
* if the new request is sync, but the currently running queue is
* not, let the sync request have priority.
*/
if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
return 1;
/*
* So both queues are sync. Let the new request get disk time if
* it's a metadata request and the current queue is doing regular IO.
*/
if (rq_is_meta(rq) && !cfqq->meta_pending)
return 1;
return 0;
}
/*
* cfqq preempts the active queue. if we allowed preempt with no slice left,
* let it have half of its nominal slice.
*/
static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
cfq_slice_expired(cfqd, 1);
if (!cfqq->slice_left)
cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;
/*
* Put the new queue at the front of the of the current list,
* so we know that it will be selected next.
*/
BUG_ON(!cfq_cfqq_on_rr(cfqq));
list_move(&cfqq->cfq_list, &cfqd->cur_rr);
cfqq->slice_end = cfqq->slice_left + jiffies;
}
/*
* Called when a new fs request (rq) is added (to cfqq). Check if there's
* something we should do about it
*/
static void
cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct request *rq)
{
struct cfq_io_context *cic = RQ_CIC(rq);
if (rq_is_meta(rq))
cfqq->meta_pending++;
/*
* check if this request is a better next-serve candidate)) {
*/
cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq);
BUG_ON(!cfqq->next_rq);
/*
* we never wait for an async request and we don't allow preemption
* of an async request. so just return early
*/
if (!rq_is_sync(rq)) {
/*
* sync process issued an async request, if it's waiting
* then expire it and kick rq handling.
*/
if (cic == cfqd->active_cic &&
del_timer(&cfqd->idle_slice_timer)) {
cfq_slice_expired(cfqd, 0);
blk_start_queueing(cfqd->queue);
}
return;
}
cfq_update_io_thinktime(cfqd, cic);
cfq_update_io_seektime(cfqd, cic, rq);
cfq_update_idle_window(cfqd, cfqq, cic);
cic->last_queue = jiffies;
cic->last_request_pos = rq->sector + rq->nr_sectors;
if (cfqq == cfqd->active_queue) {
/*
* if we are waiting for a request for this queue, let it rip
* immediately and flag that we must not expire this queue
* just now
*/
if (cfq_cfqq_wait_request(cfqq)) {
cfq_mark_cfqq_must_dispatch(cfqq);
del_timer(&cfqd->idle_slice_timer);
blk_start_queueing(cfqd->queue);
}
} else if (cfq_should_preempt(cfqd, cfqq, rq)) {
/*
* not the active queue - expire current slice if it is
* idle and has expired it's mean thinktime or this new queue
* has some old slice time left and is of higher priority
*/
cfq_preempt_queue(cfqd, cfqq);
cfq_mark_cfqq_must_dispatch(cfqq);
blk_start_queueing(cfqd->queue);
}
}
static void cfq_insert_request(request_queue_t *q, struct request *rq)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_queue *cfqq = RQ_CFQQ(rq);
cfq_init_prio_data(cfqq);
cfq_add_rq_rb(rq);
list_add_tail(&rq->queuelist, &cfqq->fifo);
cfq_rq_enqueued(cfqd, cfqq, rq);
}
static void cfq_completed_request(request_queue_t *q, struct request *rq)
{
struct cfq_queue *cfqq = RQ_CFQQ(rq);
struct cfq_data *cfqd = cfqq->cfqd;
const int sync = rq_is_sync(rq);
unsigned long now;
now = jiffies;
WARN_ON(!cfqd->rq_in_driver);
WARN_ON(!cfqq->on_dispatch[sync]);
cfqd->rq_in_driver--;
cfqq->on_dispatch[sync]--;
if (!cfq_class_idle(cfqq))
cfqd->last_end_request = now;
if (!cfq_cfqq_dispatched(cfqq) && cfq_cfqq_on_rr(cfqq))
cfq_resort_rr_list(cfqq, 0);
if (sync)
RQ_CIC(rq)->last_end_request = now;
/*
* If this is the active queue, check if it needs to be expired,
* or if we want to idle in case it has no pending requests.
*/
if (cfqd->active_queue == cfqq) {
if (time_after(now, cfqq->slice_end))
cfq_slice_expired(cfqd, 0);
else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list)) {
if (!cfq_arm_slice_timer(cfqd, cfqq))
cfq_schedule_dispatch(cfqd);
}
}
}
/*
* we temporarily boost lower priority queues if they are holding fs exclusive
* resources. they are boosted to normal prio (CLASS_BE/4)
*/
static void cfq_prio_boost(struct cfq_queue *cfqq)
{
const int ioprio_class = cfqq->ioprio_class;
const int ioprio = cfqq->ioprio;
if (has_fs_excl()) {
/*
* boost idle prio on transactions that would lock out other
* users of the filesystem
*/
if (cfq_class_idle(cfqq))
cfqq->ioprio_class = IOPRIO_CLASS_BE;
if (cfqq->ioprio > IOPRIO_NORM)
cfqq->ioprio = IOPRIO_NORM;
} else {
/*
* check if we need to unboost the queue
*/
if (cfqq->ioprio_class != cfqq->org_ioprio_class)
cfqq->ioprio_class = cfqq->org_ioprio_class;
if (cfqq->ioprio != cfqq->org_ioprio)
cfqq->ioprio = cfqq->org_ioprio;
}
/*
* refile between round-robin lists if we moved the priority class
*/
if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio) &&
cfq_cfqq_on_rr(cfqq))
cfq_resort_rr_list(cfqq, 0);
}
static inline int __cfq_may_queue(struct cfq_queue *cfqq)
{
if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
!cfq_cfqq_must_alloc_slice(cfqq)) {
cfq_mark_cfqq_must_alloc_slice(cfqq);
return ELV_MQUEUE_MUST;
}
return ELV_MQUEUE_MAY;
}
static int cfq_may_queue(request_queue_t *q, int rw)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct task_struct *tsk = current;
struct cfq_queue *cfqq;
/*
* don't force setup of a queue from here, as a call to may_queue
* does not necessarily imply that a request actually will be queued.
* so just lookup a possibly existing queue, or return 'may queue'
* if that fails
*/
cfqq = cfq_find_cfq_hash(cfqd, cfq_queue_pid(tsk, rw), tsk->ioprio);
if (cfqq) {
cfq_init_prio_data(cfqq);
cfq_prio_boost(cfqq);
return __cfq_may_queue(cfqq);
}
return ELV_MQUEUE_MAY;
}
/*
* queue lock held here
*/
static void cfq_put_request(request_queue_t *q, struct request *rq)
{
struct cfq_queue *cfqq = RQ_CFQQ(rq);
if (cfqq) {
const int rw = rq_data_dir(rq);
BUG_ON(!cfqq->allocated[rw]);
cfqq->allocated[rw]--;
put_io_context(RQ_CIC(rq)->ioc);
rq->elevator_private = NULL;
rq->elevator_private2 = NULL;
cfq_put_queue(cfqq);
}
}
/*
* Allocate cfq data structures associated with this request.
*/
static int
cfq_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct task_struct *tsk = current;
struct cfq_io_context *cic;
const int rw = rq_data_dir(rq);
pid_t key = cfq_queue_pid(tsk, rw);
struct cfq_queue *cfqq;
unsigned long flags;
int is_sync = key != CFQ_KEY_ASYNC;
might_sleep_if(gfp_mask & __GFP_WAIT);
cic = cfq_get_io_context(cfqd, gfp_mask);
spin_lock_irqsave(q->queue_lock, flags);
if (!cic)
goto queue_fail;
if (!cic->cfqq[is_sync]) {
cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask);
if (!cfqq)
goto queue_fail;
cic->cfqq[is_sync] = cfqq;
} else
cfqq = cic->cfqq[is_sync];
cfqq->allocated[rw]++;
cfq_clear_cfqq_must_alloc(cfqq);
atomic_inc(&cfqq->ref);
spin_unlock_irqrestore(q->queue_lock, flags);
rq->elevator_private = cic;
rq->elevator_private2 = cfqq;
return 0;
queue_fail:
if (cic)
put_io_context(cic->ioc);
cfq_schedule_dispatch(cfqd);
spin_unlock_irqrestore(q->queue_lock, flags);
return 1;
}
static void cfq_kick_queue(void *data)
{
request_queue_t *q = data;
unsigned long flags;
spin_lock_irqsave(q->queue_lock, flags);
blk_start_queueing(q);
spin_unlock_irqrestore(q->queue_lock, flags);
}
/*
* Timer running if the active_queue is currently idling inside its time slice
*/
static void cfq_idle_slice_timer(unsigned long data)
{
struct cfq_data *cfqd = (struct cfq_data *) data;
struct cfq_queue *cfqq;
unsigned long flags;
spin_lock_irqsave(cfqd->queue->queue_lock, flags);
if ((cfqq = cfqd->active_queue) != NULL) {
unsigned long now = jiffies;
/*
* expired
*/
if (time_after(now, cfqq->slice_end))
goto expire;
/*
* only expire and reinvoke request handler, if there are
* other queues with pending requests
*/
if (!cfqd->busy_queues)
goto out_cont;
/*
* not expired and it has a request pending, let it dispatch
*/
if (!RB_EMPTY_ROOT(&cfqq->sort_list)) {
cfq_mark_cfqq_must_dispatch(cfqq);
goto out_kick;
}
}
expire:
cfq_slice_expired(cfqd, 0);
out_kick:
cfq_schedule_dispatch(cfqd);
out_cont:
spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}
/*
* Timer running if an idle class queue is waiting for service
*/
static void cfq_idle_class_timer(unsigned long data)
{
struct cfq_data *cfqd = (struct cfq_data *) data;
unsigned long flags, end;
spin_lock_irqsave(cfqd->queue->queue_lock, flags);
/*
* race with a non-idle queue, reset timer
*/
end = cfqd->last_end_request + CFQ_IDLE_GRACE;
if (!time_after_eq(jiffies, end))
mod_timer(&cfqd->idle_class_timer, end);
else
cfq_schedule_dispatch(cfqd);
spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}
static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
{
del_timer_sync(&cfqd->idle_slice_timer);
del_timer_sync(&cfqd->idle_class_timer);
blk_sync_queue(cfqd->queue);
}
static void cfq_exit_queue(elevator_t *e)
{
struct cfq_data *cfqd = e->elevator_data;
request_queue_t *q = cfqd->queue;
cfq_shutdown_timer_wq(cfqd);
spin_lock_irq(q->queue_lock);
if (cfqd->active_queue)
__cfq_slice_expired(cfqd, cfqd->active_queue, 0);
while (!list_empty(&cfqd->cic_list)) {
struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
struct cfq_io_context,
queue_list);
__cfq_exit_single_io_context(cfqd, cic);
}
spin_unlock_irq(q->queue_lock);
cfq_shutdown_timer_wq(cfqd);
kfree(cfqd->cfq_hash);
kfree(cfqd);
}
static void *cfq_init_queue(request_queue_t *q, elevator_t *e)
{
struct cfq_data *cfqd;
int i;
cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL, q->node);
if (!cfqd)
return NULL;
memset(cfqd, 0, sizeof(*cfqd));
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);
cfqd->cfq_hash = kmalloc_node(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL, q->node);
if (!cfqd->cfq_hash)
goto out_free;
for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
cfqd->queue = q;
init_timer(&cfqd->idle_slice_timer);
cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
cfqd->idle_slice_timer.data = (unsigned long) cfqd;
init_timer(&cfqd->idle_class_timer);
cfqd->idle_class_timer.function = cfq_idle_class_timer;
cfqd->idle_class_timer.data = (unsigned long) cfqd;
INIT_WORK(&cfqd->unplug_work, cfq_kick_queue, q);
cfqd->cfq_quantum = cfq_quantum;
cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
cfqd->cfq_back_max = cfq_back_max;
cfqd->cfq_back_penalty = cfq_back_penalty;
cfqd->cfq_slice[0] = cfq_slice_async;
cfqd->cfq_slice[1] = cfq_slice_sync;
cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
cfqd->cfq_slice_idle = cfq_slice_idle;
return cfqd;
out_free:
kfree(cfqd);
return NULL;
}
static void cfq_slab_kill(void)
{
if (cfq_pool)
kmem_cache_destroy(cfq_pool);
if (cfq_ioc_pool)
kmem_cache_destroy(cfq_ioc_pool);
}
static int __init cfq_slab_setup(void)
{
cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
NULL, NULL);
if (!cfq_pool)
goto fail;
cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
if (!cfq_ioc_pool)
goto fail;
return 0;
fail:
cfq_slab_kill();
return -ENOMEM;
}
/*
* sysfs parts below -->
*/
static ssize_t
cfq_var_show(unsigned int var, char *page)
{
return sprintf(page, "%d\n", var);
}
static ssize_t
cfq_var_store(unsigned int *var, const char *page, size_t count)
{
char *p = (char *) page;
*var = simple_strtoul(p, &p, 10);
return count;
}
#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
static ssize_t __FUNC(elevator_t *e, char *page) \
{ \
struct cfq_data *cfqd = e->elevator_data; \
unsigned int __data = __VAR; \
if (__CONV) \
__data = jiffies_to_msecs(__data); \
return cfq_var_show(__data, (page)); \
}
SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
#undef SHOW_FUNCTION
#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
{ \
struct cfq_data *cfqd = e->elevator_data; \
unsigned int __data; \
int ret = cfq_var_store(&__data, (page), count); \
if (__data < (MIN)) \
__data = (MIN); \
else if (__data > (MAX)) \
__data = (MAX); \
if (__CONV) \
*(__PTR) = msecs_to_jiffies(__data); \
else \
*(__PTR) = __data; \
return ret; \
}
STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
#undef STORE_FUNCTION
#define CFQ_ATTR(name) \
__ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
static struct elv_fs_entry cfq_attrs[] = {
CFQ_ATTR(quantum),
CFQ_ATTR(fifo_expire_sync),
CFQ_ATTR(fifo_expire_async),
CFQ_ATTR(back_seek_max),
CFQ_ATTR(back_seek_penalty),
CFQ_ATTR(slice_sync),
CFQ_ATTR(slice_async),
CFQ_ATTR(slice_async_rq),
CFQ_ATTR(slice_idle),
__ATTR_NULL
};
static struct elevator_type iosched_cfq = {
.ops = {
.elevator_merge_fn = cfq_merge,
.elevator_merged_fn = cfq_merged_request,
.elevator_merge_req_fn = cfq_merged_requests,
.elevator_dispatch_fn = cfq_dispatch_requests,
.elevator_add_req_fn = cfq_insert_request,
.elevator_activate_req_fn = cfq_activate_request,
.elevator_deactivate_req_fn = cfq_deactivate_request,
.elevator_queue_empty_fn = cfq_queue_empty,
.elevator_completed_req_fn = cfq_completed_request,
.elevator_former_req_fn = elv_rb_former_request,
.elevator_latter_req_fn = elv_rb_latter_request,
.elevator_set_req_fn = cfq_set_request,
.elevator_put_req_fn = cfq_put_request,
.elevator_may_queue_fn = cfq_may_queue,
.elevator_init_fn = cfq_init_queue,
.elevator_exit_fn = cfq_exit_queue,
.trim = cfq_free_io_context,
},
.elevator_attrs = cfq_attrs,
.elevator_name = "cfq",
.elevator_owner = THIS_MODULE,
};
static int __init cfq_init(void)
{
int ret;
/*
* could be 0 on HZ < 1000 setups
*/
if (!cfq_slice_async)
cfq_slice_async = 1;
if (!cfq_slice_idle)
cfq_slice_idle = 1;
if (cfq_slab_setup())
return -ENOMEM;
ret = elv_register(&iosched_cfq);
if (ret)
cfq_slab_kill();
return ret;
}
static void __exit cfq_exit(void)
{
DECLARE_COMPLETION_ONSTACK(all_gone);
elv_unregister(&iosched_cfq);
ioc_gone = &all_gone;
/* ioc_gone's update must be visible before reading ioc_count */
smp_wmb();
if (elv_ioc_count_read(ioc_count))
wait_for_completion(ioc_gone);
synchronize_rcu();
cfq_slab_kill();
}
module_init(cfq_init);
module_exit(cfq_exit);
MODULE_AUTHOR("Jens Axboe");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");