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linux-sg2042/block/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@kernel.dk>
*/
#include <linux/module.h>
#include <linux/blkdev.h>
#include <linux/elevator.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;
/*
* grace period before allowing idle class to get disk access
*/
#define CFQ_IDLE_GRACE (HZ / 10)
/*
* below this threshold, we consider thinktime immediate
*/
#define CFQ_MIN_TT (2)
#define CFQ_SLICE_SCALE (5)
#define RQ_CIC(rq) ((struct cfq_io_context*)(rq)->elevator_private)
#define RQ_CFQQ(rq) ((rq)->elevator_private2)
static struct kmem_cache *cfq_pool;
static struct kmem_cache *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 sample_valid(samples) ((samples) > 80)
/*
* Most of our rbtree usage is for sorting with min extraction, so
* if we cache the leftmost node we don't have to walk down the tree
* to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
* move this into the elevator for the rq sorting as well.
*/
struct cfq_rb_root {
struct rb_root rb;
struct rb_node *left;
};
#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, }
/*
* Per block device queue structure
*/
struct cfq_data {
request_queue_t *queue;
/*
* rr list of queues with requests and the count of them
*/
struct cfq_rb_root service_tree;
unsigned int busy_queues;
int rq_in_driver;
int sync_flight;
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;
struct cfq_queue *async_cfqq[IOPRIO_BE_NR];
struct timer_list idle_class_timer;
sector_t last_position;
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;
sector_t new_seek_mean;
u64 new_seek_total;
};
/*
* Per process-grouping structure
*/
struct cfq_queue {
/* reference count */
atomic_t ref;
/* parent cfq_data */
struct cfq_data *cfqd;
/* service_tree member */
struct rb_node rb_node;
/* service_tree key */
unsigned long rb_key;
/* 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_end;
long slice_resid;
/* number of requests that are on the dispatch list or inside driver */
int dispatched;
/* 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;
sector_t last_request_pos;
};
enum cfqq_state_flags {
CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
CFQ_CFQQ_FLAG_must_alloc, /* must be allowed rq alloc */
CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
CFQ_CFQQ_FLAG_must_dispatch, /* must dispatch, even if expired */
CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
CFQ_CFQQ_FLAG_queue_new, /* queue never been serviced */
CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
CFQ_CFQQ_FLAG_sync, /* synchronous queue */
};
#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);
CFQ_CFQQ_FNS(slice_new);
CFQ_CFQQ_FNS(sync);
#undef CFQ_CFQQ_FNS
static void cfq_dispatch_insert(request_queue_t *, struct request *);
static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
struct task_struct *, gfp_t);
static struct cfq_io_context *cfq_cic_rb_lookup(struct cfq_data *,
struct io_context *);
static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
int is_sync)
{
return cic->cfqq[!!is_sync];
}
static inline void cic_set_cfqq(struct cfq_io_context *cic,
struct cfq_queue *cfqq, int is_sync)
{
cic->cfqq[!!is_sync] = cfqq;
}
/*
* We regard a request as SYNC, if it's either a read or has the SYNC bit
* set (in which case it could also be direct WRITE).
*/
static inline int cfq_bio_sync(struct bio *bio)
{
if (bio_data_dir(bio) == READ || bio_sync(bio))
return 1;
return 0;
}
/*
* 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;
}
/*
* 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_slice(struct cfq_data *cfqd, int sync,
unsigned short prio)
{
const int base_slice = cfqd->cfq_slice[sync];
WARN_ON(prio >= IOPRIO_BE_NR);
return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
}
static inline int
cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), 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;
}
/*
* We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
* isn't valid until the first request from the dispatch is activated
* and the slice time set.
*/
static inline int cfq_slice_used(struct cfq_queue *cfqq)
{
if (cfq_cfqq_slice_new(cfqq))
return 0;
if (time_before(jiffies, cfqq->slice_end))
return 0;
return 1;
}
/*
* 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_position;
/*
* 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;
}
}
/*
* The below is leftmost cache rbtree addon
*/
static struct rb_node *cfq_rb_first(struct cfq_rb_root *root)
{
if (!root->left)
root->left = rb_first(&root->rb);
return root->left;
}
static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
{
if (root->left == n)
root->left = NULL;
rb_erase(n, &root->rb);
RB_CLEAR_NODE(n);
}
/*
* 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 unsigned long cfq_slice_offset(struct cfq_data *cfqd,
struct cfq_queue *cfqq)
{
/*
* just an approximation, should be ok.
*/
return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
}
/*
* The cfqd->service_tree holds all pending cfq_queue's that have
* requests waiting to be processed. It is sorted in the order that
* we will service the queues.
*/
static void cfq_service_tree_add(struct cfq_data *cfqd,
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;
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)) {
/*
* same position, nothing more to do
*/
if (rb_key == cfqq->rb_key)
return;
cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
}
left = 1;
while (*p) {
struct cfq_queue *__cfqq;
struct rb_node **n;
parent = *p;
__cfqq = rb_entry(parent, struct cfq_queue, rb_node);
/*
* sort RT queues first, we always want to give
* preference to them. IDLE queues goes to the back.
* after that, sort on the next service time.
*/
if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
n = &(*p)->rb_left;
else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
n = &(*p)->rb_right;
else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq))
n = &(*p)->rb_left;
else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
n = &(*p)->rb_right;
else if (rb_key < __cfqq->rb_key)
n = &(*p)->rb_left;
else
n = &(*p)->rb_right;
if (n == &(*p)->rb_right)
left = 0;
p = n;
}
if (left)
cfqd->service_tree.left = &cfqq->rb_node;
cfqq->rb_key = rb_key;
rb_link_node(&cfqq->rb_node, parent, p);
rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
}
/*
* Update cfqq's position in the service tree.
*/
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(cfqd, cfqq, 0);
}
/*
* 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(cfqd, cfqq);
}
/*
* Called when the cfqq no longer has requests pending, remove it from
* the service tree.
*/
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);
if (!RB_EMPTY_NODE(&cfqq->rb_node))
cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
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);
/*
* 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);
}
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;
struct cfq_io_context *cic;
struct cfq_queue *cfqq;
cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
if (!cic)
return NULL;
cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
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;
cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors;
}
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 int cfq_allow_merge(request_queue_t *q, struct request *rq,
struct bio *bio)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_io_context *cic;
struct cfq_queue *cfqq;
/*
* Disallow merge of a sync bio into an async request.
*/
if (cfq_bio_sync(bio) && !rq_is_sync(rq))
return 0;
/*
* Lookup the cfqq that this bio will be queued with. Allow
* merge only if rq is queued there.
*/
cic = cfq_cic_rb_lookup(cfqd, current->io_context);
if (!cic)
return 0;
cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
if (cfqq == RQ_CFQQ(rq))
return 1;
return 0;
}
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_end = 0;
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);
}
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 timed_out)
{
if (cfq_cfqq_wait_request(cfqq))
del_timer(&cfqd->idle_slice_timer);
cfq_clear_cfqq_must_dispatch(cfqq);
cfq_clear_cfqq_wait_request(cfqq);
/*
* store what was left of this slice, if the queue idled/timed out
*/
if (timed_out && !cfq_cfqq_slice_new(cfqq))
cfqq->slice_resid = cfqq->slice_end - jiffies;
cfq_resort_rr_list(cfqd, cfqq);
if (cfqq == cfqd->active_queue)
cfqd->active_queue = NULL;
if (cfqd->active_cic) {
put_io_context(cfqd->active_cic->ioc);
cfqd->active_cic = NULL;
}
}
static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
{
struct cfq_queue *cfqq = cfqd->active_queue;
if (cfqq)
__cfq_slice_expired(cfqd, cfqq, timed_out);
}
/*
* Get next queue for service. Unless we have a queue preemption,
* we'll simply select the first cfqq in the service tree.
*/
static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq;
struct rb_node *n;
if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
return NULL;
n = cfq_rb_first(&cfqd->service_tree);
cfqq = rb_entry(n, struct cfq_queue, rb_node);
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;
}
}
return cfqq;
}
/*
* Get and set a new active queue for service.
*/
static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq;
cfqq = cfq_get_next_queue(cfqd);
__cfq_set_active_queue(cfqd, cfqq);
return cfqq;
}
static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
struct request *rq)
{
if (rq->sector >= cfqd->last_position)
return rq->sector - cfqd->last_position;
else
return cfqd->last_position - rq->sector;
}
static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
{
struct cfq_io_context *cic = cfqd->active_cic;
if (!sample_valid(cic->seek_samples))
return 0;
return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean;
}
static int cfq_close_cooperator(struct cfq_data *cfq_data,
struct cfq_queue *cfqq)
{
/*
* We should notice if some of the queues are cooperating, eg
* working closely on the same area of the disk. In that case,
* we can group them together and don't waste time idling.
*/
return 0;
}
#define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
static void cfq_arm_slice_timer(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq = cfqd->active_queue;
struct cfq_io_context *cic;
unsigned long sl;
WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
WARN_ON(cfq_cfqq_slice_new(cfqq));
/*
* idle is disabled, either manually or by past process history
*/
if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq))
return;
/*
* task has exited, don't wait
*/
cic = cfqd->active_cic;
if (!cic || !cic->ioc->task)
return;
/*
* See if this prio level has a good candidate
*/
if (cfq_close_cooperator(cfqd, cfqq) &&
(sample_valid(cic->ttime_samples) && cic->ttime_mean > 2))
return;
cfq_mark_cfqq_must_dispatch(cfqq);
cfq_mark_cfqq_wait_request(cfqq);
/*
* 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
*/
sl = cfqd->cfq_slice_idle;
if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
}
/*
* Move request from internal lists to the request queue dispatch list.
*/
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->dispatched++;
elv_dispatch_sort(q, rq);
if (cfq_cfqq_sync(cfqq))
cfqd->sync_flight++;
}
/*
* 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;
cfq_mark_cfqq_fifo_expire(cfqq);
if (list_empty(&cfqq->fifo))
return NULL;
fifo = cfq_cfqq_sync(cfqq);
rq = rq_entry_fifo(cfqq->fifo.next);
if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
return NULL;
return rq;
}
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));
}
/*
* Select a queue for service. If we have a current active queue,
* check whether to continue servicing it, or retrieve and set a new one.
*/
static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq;
cfqq = cfqd->active_queue;
if (!cfqq)
goto new_queue;
/*
* The active queue has run out of time, expire it and select new.
*/
if (cfq_slice_used(cfqq))
goto expire;
/*
* The active queue has requests and isn't expired, allow it to
* dispatch.
*/
if (!RB_EMPTY_ROOT(&cfqq->sort_list))
goto keep_queue;
/*
* No requests pending. If the active queue still has requests in
* flight or is idling for a new request, allow either of these
* conditions to happen (or time out) before selecting a new queue.
*/
if (timer_pending(&cfqd->idle_slice_timer) ||
(cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) {
cfqq = NULL;
goto keep_queue;
}
expire:
cfq_slice_expired(cfqd, 0);
new_queue:
cfqq = cfq_set_active_queue(cfqd);
keep_queue:
return cfqq;
}
/*
* Dispatch some requests from cfqq, moving them to the request queue
* dispatch list.
*/
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);
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);
/*
* expire an async queue immediately if it has used up its slice. idle
* queue always expire after 1 dispatch round.
*/
if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
dispatched >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
cfq_class_idle(cfqq))) {
cfqq->slice_end = jiffies + 1;
cfq_slice_expired(cfqd, 0);
}
return dispatched;
}
static inline int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
{
int dispatched = 0;
while (cfqq->next_rq) {
cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
dispatched++;
}
BUG_ON(!list_empty(&cfqq->fifo));
return dispatched;
}
/*
* Drain our current requests. Used for barriers and when switching
* io schedulers on-the-fly.
*/
static int cfq_forced_dispatch(struct cfq_data *cfqd)
{
int dispatched = 0;
struct rb_node *n;
while ((n = cfq_rb_first(&cfqd->service_tree)) != NULL) {
struct cfq_queue *cfqq = rb_entry(n, struct cfq_queue, rb_node);
dispatched += __cfq_forced_dispatch_cfqq(cfqq);
}
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;
int dispatched;
if (!cfqd->busy_queues)
return 0;
if (unlikely(force))
return cfq_forced_dispatch(cfqd);
dispatched = 0;
while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
int max_dispatch;
max_dispatch = cfqd->cfq_quantum;
if (cfq_class_idle(cfqq))
max_dispatch = 1;
if (cfqq->dispatched >= max_dispatch) {
if (cfqd->busy_queues > 1)
break;
if (cfqq->dispatched >= 4 * max_dispatch)
break;
}
if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
break;
cfq_clear_cfqq_must_dispatch(cfqq);
cfq_clear_cfqq_wait_request(cfqq);
del_timer(&cfqd->idle_slice_timer);
dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
}
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);
cfq_schedule_dispatch(cfqd);
}
kmem_cache_free(cfq_pool, cfqq);
}
static void cfq_free_io_context(struct io_context *ioc)
{
struct cfq_io_context *__cic;
struct rb_node *n;
int freed = 0;
ioc->ioc_data = NULL;
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_schedule_dispatch(cfqd);
}
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;
}
}
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);
}
}
/*
* The process that ioc belongs to has exited, we need to clean up
* and put the internal structures we have that belongs to that process.
*/
static void cfq_exit_io_context(struct io_context *ioc)
{
struct cfq_io_context *__cic;
struct rb_node *n;
ioc->ioc_data = NULL;
/*
* 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 | __GFP_ZERO,
cfqd->queue->node);
if (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;
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, 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_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
struct task_struct *tsk, gfp_t gfp_mask)
{
struct cfq_queue *cfqq, *new_cfqq = NULL;
struct cfq_io_context *cic;
retry:
cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
/* cic always exists here */
cfqq = cic_to_cfqq(cic, is_sync);
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 | __GFP_ZERO,
cfqd->queue->node);
spin_lock_irq(cfqd->queue->queue_lock);
goto retry;
} else {
cfqq = kmem_cache_alloc_node(cfq_pool,
gfp_mask | __GFP_ZERO,
cfqd->queue->node);
if (!cfqq)
goto out;
}
RB_CLEAR_NODE(&cfqq->rb_node);
INIT_LIST_HEAD(&cfqq->fifo);
atomic_set(&cfqq->ref, 0);
cfqq->cfqd = cfqd;
if (is_sync) {
cfq_mark_cfqq_idle_window(cfqq);
cfq_mark_cfqq_sync(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);
out:
WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
return cfqq;
}
static struct cfq_queue *
cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
gfp_t gfp_mask)
{
const int ioprio = task_ioprio(tsk);
struct cfq_queue *cfqq = NULL;
if (!is_sync)
cfqq = cfqd->async_cfqq[ioprio];
if (!cfqq)
cfqq = cfq_find_alloc_queue(cfqd, is_sync, tsk, gfp_mask);
/*
* pin the queue now that it's allocated, scheduler exit will prune it
*/
if (!is_sync && !cfqd->async_cfqq[ioprio]) {
atomic_inc(&cfqq->ref);
cfqd->async_cfqq[ioprio] = cfqq;
}
atomic_inc(&cfqq->ref);
return cfqq;
}
/*
* We drop cfq io contexts lazily, so we may find a dead one.
*/
static void
cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
{
WARN_ON(!list_empty(&cic->queue_list));
if (ioc->ioc_data == cic)
ioc->ioc_data = NULL;
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;
if (unlikely(!ioc))
return NULL;
/*
* we maintain a last-hit cache, to avoid browsing over the tree
*/
cic = ioc->ioc_data;
if (cic && cic->key == cfqd)
return cic;
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 {
ioc->ioc_data = cic;
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 = jiffies - cic->last_end_request;
unsigned long 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;
if (!cic->seek_samples) {
cfqd->new_seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
cfqd->new_seek_mean = cfqd->new_seek_total / 256;
}
/*
* 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;
if (!cfq_cfqq_sync(cfqq))
return;
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;
cfqq = cfqd->active_queue;
if (!cfqq)
return 0;
if (cfq_slice_used(cfqq))
return 1;
if (cfq_class_idle(new_cfqq))
return 0;
if (cfq_class_idle(cfqq))
return 1;
/*
* 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;
if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
return 0;
/*
* if this request is as-good as one we would expect from the
* current cfqq, let it preempt
*/
if (cfq_rq_close(cfqd, rq))
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);
/*
* 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));
cfq_service_tree_add(cfqd, cfqq, 1);
cfqq->slice_end = 0;
cfq_mark_cfqq_slice_new(cfqq);
}
/*
* 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++;
cfq_update_io_thinktime(cfqd, cic);
cfq_update_io_seektime(cfqd, cic, rq);
cfq_update_idle_window(cfqd, cfqq, cic);
cic->last_request_pos = rq->sector + rq->nr_sectors;
cfqq->last_request_pos = cic->last_request_pos;
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->dispatched);
cfqd->rq_in_driver--;
cfqq->dispatched--;
if (cfq_cfqq_sync(cfqq))
cfqd->sync_flight--;
if (!cfq_class_idle(cfqq))
cfqd->last_end_request = now;
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 (cfq_cfqq_slice_new(cfqq)) {
cfq_set_prio_slice(cfqd, cfqq);
cfq_clear_cfqq_slice_new(cfqq);
}
if (cfq_slice_used(cfqq))
cfq_slice_expired(cfqd, 1);
else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list))
cfq_arm_slice_timer(cfqd);
}
if (!cfqd->rq_in_driver)
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)
{
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;
}
}
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_io_context *cic;
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
*/
cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
if (!cic)
return ELV_MQUEUE_MAY;
cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC);
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(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);
const int is_sync = rq_is_sync(rq);
struct cfq_queue *cfqq;
unsigned long flags;
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;
cfqq = cic_to_cfqq(cic, is_sync);
if (!cfqq) {
cfqq = cfq_get_queue(cfqd, is_sync, tsk, gfp_mask);
if (!cfqq)
goto queue_fail;
cic_set_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(struct work_struct *work)
{
struct cfq_data *cfqd =
container_of(work, struct cfq_data, unplug_work);
request_queue_t *q = cfqd->queue;
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;
int timed_out = 1;
spin_lock_irqsave(cfqd->queue->queue_lock, flags);
if ((cfqq = cfqd->active_queue) != NULL) {
timed_out = 0;
/*
* expired
*/
if (cfq_slice_used(cfqq))
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, timed_out);
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;
int i;
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);
}
/*
* Put the async queues
*/
for (i = 0; i < IOPRIO_BE_NR; i++)
if (cfqd->async_cfqq[i])
cfq_put_queue(cfqd->async_cfqq[i]);
spin_unlock_irq(q->queue_lock);
cfq_shutdown_timer_wq(cfqd);
kfree(cfqd);
}
static void *cfq_init_queue(request_queue_t *q)
{
struct cfq_data *cfqd;
cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
if (!cfqd)
return NULL;
cfqd->service_tree = CFQ_RB_ROOT;
INIT_LIST_HEAD(&cfqd->cic_list);
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);
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;
}
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(cfq_queue, 0);
if (!cfq_pool)
goto fail;
cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
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_allow_merge_fn = cfq_allow_merge,
.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");
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