| /* |
| * Anticipatory & deadline i/o scheduler. |
| * |
| * Copyright (C) 2002 Jens Axboe <axboe@suse.de> |
| * Nick Piggin <nickpiggin@yahoo.com.au> |
| * |
| */ |
| #include <linux/kernel.h> |
| #include <linux/fs.h> |
| #include <linux/blkdev.h> |
| #include <linux/elevator.h> |
| #include <linux/bio.h> |
| #include <linux/config.h> |
| #include <linux/module.h> |
| #include <linux/slab.h> |
| #include <linux/init.h> |
| #include <linux/compiler.h> |
| #include <linux/hash.h> |
| #include <linux/rbtree.h> |
| #include <linux/interrupt.h> |
| |
| #define REQ_SYNC 1 |
| #define REQ_ASYNC 0 |
| |
| /* |
| * See Documentation/block/as-iosched.txt |
| */ |
| |
| /* |
| * max time before a read is submitted. |
| */ |
| #define default_read_expire (HZ / 8) |
| |
| /* |
| * ditto for writes, these limits are not hard, even |
| * if the disk is capable of satisfying them. |
| */ |
| #define default_write_expire (HZ / 4) |
| |
| /* |
| * read_batch_expire describes how long we will allow a stream of reads to |
| * persist before looking to see whether it is time to switch over to writes. |
| */ |
| #define default_read_batch_expire (HZ / 2) |
| |
| /* |
| * write_batch_expire describes how long we want a stream of writes to run for. |
| * This is not a hard limit, but a target we set for the auto-tuning thingy. |
| * See, the problem is: we can send a lot of writes to disk cache / TCQ in |
| * a short amount of time... |
| */ |
| #define default_write_batch_expire (HZ / 8) |
| |
| /* |
| * max time we may wait to anticipate a read (default around 6ms) |
| */ |
| #define default_antic_expire ((HZ / 150) ? HZ / 150 : 1) |
| |
| /* |
| * Keep track of up to 20ms thinktimes. We can go as big as we like here, |
| * however huge values tend to interfere and not decay fast enough. A program |
| * might be in a non-io phase of operation. Waiting on user input for example, |
| * or doing a lengthy computation. A small penalty can be justified there, and |
| * will still catch out those processes that constantly have large thinktimes. |
| */ |
| #define MAX_THINKTIME (HZ/50UL) |
| |
| /* Bits in as_io_context.state */ |
| enum as_io_states { |
| AS_TASK_RUNNING=0, /* Process has not exited */ |
| AS_TASK_IOSTARTED, /* Process has started some IO */ |
| AS_TASK_IORUNNING, /* Process has completed some IO */ |
| }; |
| |
| enum anticipation_status { |
| ANTIC_OFF=0, /* Not anticipating (normal operation) */ |
| ANTIC_WAIT_REQ, /* The last read has not yet completed */ |
| ANTIC_WAIT_NEXT, /* Currently anticipating a request vs |
| last read (which has completed) */ |
| ANTIC_FINISHED, /* Anticipating but have found a candidate |
| * or timed out */ |
| }; |
| |
| struct as_data { |
| /* |
| * run time data |
| */ |
| |
| struct request_queue *q; /* the "owner" queue */ |
| |
| /* |
| * requests (as_rq s) are present on both sort_list and fifo_list |
| */ |
| struct rb_root sort_list[2]; |
| struct list_head fifo_list[2]; |
| |
| struct as_rq *next_arq[2]; /* next in sort order */ |
| sector_t last_sector[2]; /* last REQ_SYNC & REQ_ASYNC sectors */ |
| struct list_head *hash; /* request hash */ |
| |
| unsigned long exit_prob; /* probability a task will exit while |
| being waited on */ |
| unsigned long exit_no_coop; /* probablility an exited task will |
| not be part of a later cooperating |
| request */ |
| unsigned long new_ttime_total; /* mean thinktime on new proc */ |
| unsigned long new_ttime_mean; |
| u64 new_seek_total; /* mean seek on new proc */ |
| sector_t new_seek_mean; |
| |
| unsigned long current_batch_expires; |
| unsigned long last_check_fifo[2]; |
| int changed_batch; /* 1: waiting for old batch to end */ |
| int new_batch; /* 1: waiting on first read complete */ |
| int batch_data_dir; /* current batch REQ_SYNC / REQ_ASYNC */ |
| int write_batch_count; /* max # of reqs in a write batch */ |
| int current_write_count; /* how many requests left this batch */ |
| int write_batch_idled; /* has the write batch gone idle? */ |
| mempool_t *arq_pool; |
| |
| enum anticipation_status antic_status; |
| unsigned long antic_start; /* jiffies: when it started */ |
| struct timer_list antic_timer; /* anticipatory scheduling timer */ |
| struct work_struct antic_work; /* Deferred unplugging */ |
| struct io_context *io_context; /* Identify the expected process */ |
| int ioc_finished; /* IO associated with io_context is finished */ |
| int nr_dispatched; |
| |
| /* |
| * settings that change how the i/o scheduler behaves |
| */ |
| unsigned long fifo_expire[2]; |
| unsigned long batch_expire[2]; |
| unsigned long antic_expire; |
| }; |
| |
| #define list_entry_fifo(ptr) list_entry((ptr), struct as_rq, fifo) |
| |
| /* |
| * per-request data. |
| */ |
| enum arq_state { |
| AS_RQ_NEW=0, /* New - not referenced and not on any lists */ |
| AS_RQ_QUEUED, /* In the request queue. It belongs to the |
| scheduler */ |
| AS_RQ_DISPATCHED, /* On the dispatch list. It belongs to the |
| driver now */ |
| AS_RQ_PRESCHED, /* Debug poisoning for requests being used */ |
| AS_RQ_REMOVED, |
| AS_RQ_MERGED, |
| AS_RQ_POSTSCHED, /* when they shouldn't be */ |
| }; |
| |
| struct as_rq { |
| /* |
| * rbtree index, key is the starting offset |
| */ |
| struct rb_node rb_node; |
| sector_t rb_key; |
| |
| struct request *request; |
| |
| struct io_context *io_context; /* The submitting task */ |
| |
| /* |
| * request hash, key is the ending offset (for back merge lookup) |
| */ |
| struct list_head hash; |
| unsigned int on_hash; |
| |
| /* |
| * expire fifo |
| */ |
| struct list_head fifo; |
| unsigned long expires; |
| |
| unsigned int is_sync; |
| enum arq_state state; |
| }; |
| |
| #define RQ_DATA(rq) ((struct as_rq *) (rq)->elevator_private) |
| |
| static kmem_cache_t *arq_pool; |
| |
| static atomic_t ioc_count = ATOMIC_INIT(0); |
| static struct completion *ioc_gone; |
| |
| static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq); |
| static void as_antic_stop(struct as_data *ad); |
| |
| /* |
| * IO Context helper functions |
| */ |
| |
| /* Called to deallocate the as_io_context */ |
| static void free_as_io_context(struct as_io_context *aic) |
| { |
| kfree(aic); |
| if (atomic_dec_and_test(&ioc_count) && ioc_gone) |
| complete(ioc_gone); |
| } |
| |
| static void as_trim(struct io_context *ioc) |
| { |
| if (ioc->aic) |
| free_as_io_context(ioc->aic); |
| ioc->aic = NULL; |
| } |
| |
| /* Called when the task exits */ |
| static void exit_as_io_context(struct as_io_context *aic) |
| { |
| WARN_ON(!test_bit(AS_TASK_RUNNING, &aic->state)); |
| clear_bit(AS_TASK_RUNNING, &aic->state); |
| } |
| |
| static struct as_io_context *alloc_as_io_context(void) |
| { |
| struct as_io_context *ret; |
| |
| ret = kmalloc(sizeof(*ret), GFP_ATOMIC); |
| if (ret) { |
| ret->dtor = free_as_io_context; |
| ret->exit = exit_as_io_context; |
| ret->state = 1 << AS_TASK_RUNNING; |
| atomic_set(&ret->nr_queued, 0); |
| atomic_set(&ret->nr_dispatched, 0); |
| spin_lock_init(&ret->lock); |
| ret->ttime_total = 0; |
| ret->ttime_samples = 0; |
| ret->ttime_mean = 0; |
| ret->seek_total = 0; |
| ret->seek_samples = 0; |
| ret->seek_mean = 0; |
| atomic_inc(&ioc_count); |
| } |
| |
| return ret; |
| } |
| |
| /* |
| * If the current task has no AS IO context then create one and initialise it. |
| * Then take a ref on the task's io context and return it. |
| */ |
| static struct io_context *as_get_io_context(void) |
| { |
| struct io_context *ioc = get_io_context(GFP_ATOMIC); |
| if (ioc && !ioc->aic) { |
| ioc->aic = alloc_as_io_context(); |
| if (!ioc->aic) { |
| put_io_context(ioc); |
| ioc = NULL; |
| } |
| } |
| return ioc; |
| } |
| |
| static void as_put_io_context(struct as_rq *arq) |
| { |
| struct as_io_context *aic; |
| |
| if (unlikely(!arq->io_context)) |
| return; |
| |
| aic = arq->io_context->aic; |
| |
| if (arq->is_sync == REQ_SYNC && aic) { |
| spin_lock(&aic->lock); |
| set_bit(AS_TASK_IORUNNING, &aic->state); |
| aic->last_end_request = jiffies; |
| spin_unlock(&aic->lock); |
| } |
| |
| put_io_context(arq->io_context); |
| } |
| |
| /* |
| * the back merge hash support functions |
| */ |
| static const int as_hash_shift = 6; |
| #define AS_HASH_BLOCK(sec) ((sec) >> 3) |
| #define AS_HASH_FN(sec) (hash_long(AS_HASH_BLOCK((sec)), as_hash_shift)) |
| #define AS_HASH_ENTRIES (1 << as_hash_shift) |
| #define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors) |
| #define list_entry_hash(ptr) list_entry((ptr), struct as_rq, hash) |
| |
| static inline void __as_del_arq_hash(struct as_rq *arq) |
| { |
| arq->on_hash = 0; |
| list_del_init(&arq->hash); |
| } |
| |
| static inline void as_del_arq_hash(struct as_rq *arq) |
| { |
| if (arq->on_hash) |
| __as_del_arq_hash(arq); |
| } |
| |
| static void as_add_arq_hash(struct as_data *ad, struct as_rq *arq) |
| { |
| struct request *rq = arq->request; |
| |
| BUG_ON(arq->on_hash); |
| |
| arq->on_hash = 1; |
| list_add(&arq->hash, &ad->hash[AS_HASH_FN(rq_hash_key(rq))]); |
| } |
| |
| /* |
| * move hot entry to front of chain |
| */ |
| static inline void as_hot_arq_hash(struct as_data *ad, struct as_rq *arq) |
| { |
| struct request *rq = arq->request; |
| struct list_head *head = &ad->hash[AS_HASH_FN(rq_hash_key(rq))]; |
| |
| if (!arq->on_hash) { |
| WARN_ON(1); |
| return; |
| } |
| |
| if (arq->hash.prev != head) { |
| list_del(&arq->hash); |
| list_add(&arq->hash, head); |
| } |
| } |
| |
| static struct request *as_find_arq_hash(struct as_data *ad, sector_t offset) |
| { |
| struct list_head *hash_list = &ad->hash[AS_HASH_FN(offset)]; |
| struct list_head *entry, *next = hash_list->next; |
| |
| while ((entry = next) != hash_list) { |
| struct as_rq *arq = list_entry_hash(entry); |
| struct request *__rq = arq->request; |
| |
| next = entry->next; |
| |
| BUG_ON(!arq->on_hash); |
| |
| if (!rq_mergeable(__rq)) { |
| as_del_arq_hash(arq); |
| continue; |
| } |
| |
| if (rq_hash_key(__rq) == offset) |
| return __rq; |
| } |
| |
| return NULL; |
| } |
| |
| /* |
| * rb tree support functions |
| */ |
| #define RB_EMPTY(root) ((root)->rb_node == NULL) |
| #define ON_RB(node) (rb_parent(node) != node) |
| #define RB_CLEAR(node) (rb_set_parent(node, node)) |
| #define rb_entry_arq(node) rb_entry((node), struct as_rq, rb_node) |
| #define ARQ_RB_ROOT(ad, arq) (&(ad)->sort_list[(arq)->is_sync]) |
| #define rq_rb_key(rq) (rq)->sector |
| |
| /* |
| * as_find_first_arq finds the first (lowest sector numbered) request |
| * for the specified data_dir. Used to sweep back to the start of the disk |
| * (1-way elevator) after we process the last (highest sector) request. |
| */ |
| static struct as_rq *as_find_first_arq(struct as_data *ad, int data_dir) |
| { |
| struct rb_node *n = ad->sort_list[data_dir].rb_node; |
| |
| if (n == NULL) |
| return NULL; |
| |
| for (;;) { |
| if (n->rb_left == NULL) |
| return rb_entry_arq(n); |
| |
| n = n->rb_left; |
| } |
| } |
| |
| /* |
| * Add the request to the rb tree if it is unique. If there is an alias (an |
| * existing request against the same sector), which can happen when using |
| * direct IO, then return the alias. |
| */ |
| static struct as_rq *__as_add_arq_rb(struct as_data *ad, struct as_rq *arq) |
| { |
| struct rb_node **p = &ARQ_RB_ROOT(ad, arq)->rb_node; |
| struct rb_node *parent = NULL; |
| struct as_rq *__arq; |
| struct request *rq = arq->request; |
| |
| arq->rb_key = rq_rb_key(rq); |
| |
| while (*p) { |
| parent = *p; |
| __arq = rb_entry_arq(parent); |
| |
| if (arq->rb_key < __arq->rb_key) |
| p = &(*p)->rb_left; |
| else if (arq->rb_key > __arq->rb_key) |
| p = &(*p)->rb_right; |
| else |
| return __arq; |
| } |
| |
| rb_link_node(&arq->rb_node, parent, p); |
| rb_insert_color(&arq->rb_node, ARQ_RB_ROOT(ad, arq)); |
| |
| return NULL; |
| } |
| |
| static void as_add_arq_rb(struct as_data *ad, struct as_rq *arq) |
| { |
| struct as_rq *alias; |
| |
| while ((unlikely(alias = __as_add_arq_rb(ad, arq)))) { |
| as_move_to_dispatch(ad, alias); |
| as_antic_stop(ad); |
| } |
| } |
| |
| static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq) |
| { |
| if (!ON_RB(&arq->rb_node)) { |
| WARN_ON(1); |
| return; |
| } |
| |
| rb_erase(&arq->rb_node, ARQ_RB_ROOT(ad, arq)); |
| RB_CLEAR(&arq->rb_node); |
| } |
| |
| static struct request * |
| as_find_arq_rb(struct as_data *ad, sector_t sector, int data_dir) |
| { |
| struct rb_node *n = ad->sort_list[data_dir].rb_node; |
| struct as_rq *arq; |
| |
| while (n) { |
| arq = rb_entry_arq(n); |
| |
| if (sector < arq->rb_key) |
| n = n->rb_left; |
| else if (sector > arq->rb_key) |
| n = n->rb_right; |
| else |
| return arq->request; |
| } |
| |
| return NULL; |
| } |
| |
| /* |
| * IO Scheduler proper |
| */ |
| |
| #define MAXBACK (1024 * 1024) /* |
| * Maximum distance the disk will go backward |
| * for a request. |
| */ |
| |
| #define BACK_PENALTY 2 |
| |
| /* |
| * as_choose_req selects the preferred one of two requests of the same data_dir |
| * ignoring time - eg. timeouts, which is the job of as_dispatch_request |
| */ |
| static struct as_rq * |
| as_choose_req(struct as_data *ad, struct as_rq *arq1, struct as_rq *arq2) |
| { |
| int data_dir; |
| sector_t last, s1, s2, d1, d2; |
| int r1_wrap=0, r2_wrap=0; /* requests are behind the disk head */ |
| const sector_t maxback = MAXBACK; |
| |
| if (arq1 == NULL || arq1 == arq2) |
| return arq2; |
| if (arq2 == NULL) |
| return arq1; |
| |
| data_dir = arq1->is_sync; |
| |
| last = ad->last_sector[data_dir]; |
| s1 = arq1->request->sector; |
| s2 = arq2->request->sector; |
| |
| BUG_ON(data_dir != arq2->is_sync); |
| |
| /* |
| * 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+maxback >= last) |
| d1 = (last - s1)*BACK_PENALTY; |
| else { |
| r1_wrap = 1; |
| d1 = 0; /* shut up, gcc */ |
| } |
| |
| if (s2 >= last) |
| d2 = s2 - last; |
| else if (s2+maxback >= last) |
| d2 = (last - s2)*BACK_PENALTY; |
| else { |
| r2_wrap = 1; |
| d2 = 0; |
| } |
| |
| /* Found required data */ |
| if (!r1_wrap && r2_wrap) |
| return arq1; |
| else if (!r2_wrap && r1_wrap) |
| return arq2; |
| else if (r1_wrap && r2_wrap) { |
| /* both behind the head */ |
| if (s1 <= s2) |
| return arq1; |
| else |
| return arq2; |
| } |
| |
| /* Both requests in front of the head */ |
| if (d1 < d2) |
| return arq1; |
| else if (d2 < d1) |
| return arq2; |
| else { |
| if (s1 >= s2) |
| return arq1; |
| else |
| return arq2; |
| } |
| } |
| |
| /* |
| * as_find_next_arq finds the next request after @prev in elevator order. |
| * this with as_choose_req form the basis for how the scheduler chooses |
| * what request to process next. Anticipation works on top of this. |
| */ |
| static struct as_rq *as_find_next_arq(struct as_data *ad, struct as_rq *last) |
| { |
| const int data_dir = last->is_sync; |
| struct as_rq *ret; |
| struct rb_node *rbnext = rb_next(&last->rb_node); |
| struct rb_node *rbprev = rb_prev(&last->rb_node); |
| struct as_rq *arq_next, *arq_prev; |
| |
| BUG_ON(!ON_RB(&last->rb_node)); |
| |
| if (rbprev) |
| arq_prev = rb_entry_arq(rbprev); |
| else |
| arq_prev = NULL; |
| |
| if (rbnext) |
| arq_next = rb_entry_arq(rbnext); |
| else { |
| arq_next = as_find_first_arq(ad, data_dir); |
| if (arq_next == last) |
| arq_next = NULL; |
| } |
| |
| ret = as_choose_req(ad, arq_next, arq_prev); |
| |
| return ret; |
| } |
| |
| /* |
| * anticipatory scheduling functions follow |
| */ |
| |
| /* |
| * as_antic_expired tells us when we have anticipated too long. |
| * The funny "absolute difference" math on the elapsed time is to handle |
| * jiffy wraps, and disks which have been idle for 0x80000000 jiffies. |
| */ |
| static int as_antic_expired(struct as_data *ad) |
| { |
| long delta_jif; |
| |
| delta_jif = jiffies - ad->antic_start; |
| if (unlikely(delta_jif < 0)) |
| delta_jif = -delta_jif; |
| if (delta_jif < ad->antic_expire) |
| return 0; |
| |
| return 1; |
| } |
| |
| /* |
| * as_antic_waitnext starts anticipating that a nice request will soon be |
| * submitted. See also as_antic_waitreq |
| */ |
| static void as_antic_waitnext(struct as_data *ad) |
| { |
| unsigned long timeout; |
| |
| BUG_ON(ad->antic_status != ANTIC_OFF |
| && ad->antic_status != ANTIC_WAIT_REQ); |
| |
| timeout = ad->antic_start + ad->antic_expire; |
| |
| mod_timer(&ad->antic_timer, timeout); |
| |
| ad->antic_status = ANTIC_WAIT_NEXT; |
| } |
| |
| /* |
| * as_antic_waitreq starts anticipating. We don't start timing the anticipation |
| * until the request that we're anticipating on has finished. This means we |
| * are timing from when the candidate process wakes up hopefully. |
| */ |
| static void as_antic_waitreq(struct as_data *ad) |
| { |
| BUG_ON(ad->antic_status == ANTIC_FINISHED); |
| if (ad->antic_status == ANTIC_OFF) { |
| if (!ad->io_context || ad->ioc_finished) |
| as_antic_waitnext(ad); |
| else |
| ad->antic_status = ANTIC_WAIT_REQ; |
| } |
| } |
| |
| /* |
| * This is called directly by the functions in this file to stop anticipation. |
| * We kill the timer and schedule a call to the request_fn asap. |
| */ |
| static void as_antic_stop(struct as_data *ad) |
| { |
| int status = ad->antic_status; |
| |
| if (status == ANTIC_WAIT_REQ || status == ANTIC_WAIT_NEXT) { |
| if (status == ANTIC_WAIT_NEXT) |
| del_timer(&ad->antic_timer); |
| ad->antic_status = ANTIC_FINISHED; |
| /* see as_work_handler */ |
| kblockd_schedule_work(&ad->antic_work); |
| } |
| } |
| |
| /* |
| * as_antic_timeout is the timer function set by as_antic_waitnext. |
| */ |
| static void as_antic_timeout(unsigned long data) |
| { |
| struct request_queue *q = (struct request_queue *)data; |
| struct as_data *ad = q->elevator->elevator_data; |
| unsigned long flags; |
| |
| spin_lock_irqsave(q->queue_lock, flags); |
| if (ad->antic_status == ANTIC_WAIT_REQ |
| || ad->antic_status == ANTIC_WAIT_NEXT) { |
| struct as_io_context *aic = ad->io_context->aic; |
| |
| ad->antic_status = ANTIC_FINISHED; |
| kblockd_schedule_work(&ad->antic_work); |
| |
| if (aic->ttime_samples == 0) { |
| /* process anticipated on has exited or timed out*/ |
| ad->exit_prob = (7*ad->exit_prob + 256)/8; |
| } |
| if (!test_bit(AS_TASK_RUNNING, &aic->state)) { |
| /* process not "saved" by a cooperating request */ |
| ad->exit_no_coop = (7*ad->exit_no_coop + 256)/8; |
| } |
| } |
| spin_unlock_irqrestore(q->queue_lock, flags); |
| } |
| |
| static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic, |
| unsigned long ttime) |
| { |
| /* fixed point: 1.0 == 1<<8 */ |
| if (aic->ttime_samples == 0) { |
| ad->new_ttime_total = (7*ad->new_ttime_total + 256*ttime) / 8; |
| ad->new_ttime_mean = ad->new_ttime_total / 256; |
| |
| ad->exit_prob = (7*ad->exit_prob)/8; |
| } |
| aic->ttime_samples = (7*aic->ttime_samples + 256) / 8; |
| aic->ttime_total = (7*aic->ttime_total + 256*ttime) / 8; |
| aic->ttime_mean = (aic->ttime_total + 128) / aic->ttime_samples; |
| } |
| |
| static void as_update_seekdist(struct as_data *ad, struct as_io_context *aic, |
| sector_t sdist) |
| { |
| u64 total; |
| |
| if (aic->seek_samples == 0) { |
| ad->new_seek_total = (7*ad->new_seek_total + 256*(u64)sdist)/8; |
| ad->new_seek_mean = ad->new_seek_total / 256; |
| } |
| |
| /* |
| * Don't allow the seek distance to get too large from the |
| * odd fragment, pagein, etc |
| */ |
| if (aic->seek_samples <= 60) /* second&third seek */ |
| sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*1024); |
| else |
| sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*64); |
| |
| aic->seek_samples = (7*aic->seek_samples + 256) / 8; |
| aic->seek_total = (7*aic->seek_total + (u64)256*sdist) / 8; |
| total = aic->seek_total + (aic->seek_samples/2); |
| do_div(total, aic->seek_samples); |
| aic->seek_mean = (sector_t)total; |
| } |
| |
| /* |
| * as_update_iohist keeps a decaying histogram of IO thinktimes, and |
| * updates @aic->ttime_mean based on that. It is called when a new |
| * request is queued. |
| */ |
| static void as_update_iohist(struct as_data *ad, struct as_io_context *aic, |
| struct request *rq) |
| { |
| struct as_rq *arq = RQ_DATA(rq); |
| int data_dir = arq->is_sync; |
| unsigned long thinktime = 0; |
| sector_t seek_dist; |
| |
| if (aic == NULL) |
| return; |
| |
| if (data_dir == REQ_SYNC) { |
| unsigned long in_flight = atomic_read(&aic->nr_queued) |
| + atomic_read(&aic->nr_dispatched); |
| spin_lock(&aic->lock); |
| if (test_bit(AS_TASK_IORUNNING, &aic->state) || |
| test_bit(AS_TASK_IOSTARTED, &aic->state)) { |
| /* Calculate read -> read thinktime */ |
| if (test_bit(AS_TASK_IORUNNING, &aic->state) |
| && in_flight == 0) { |
| thinktime = jiffies - aic->last_end_request; |
| thinktime = min(thinktime, MAX_THINKTIME-1); |
| } |
| as_update_thinktime(ad, aic, thinktime); |
| |
| /* Calculate read -> read seek distance */ |
| if (aic->last_request_pos < rq->sector) |
| seek_dist = rq->sector - aic->last_request_pos; |
| else |
| seek_dist = aic->last_request_pos - rq->sector; |
| as_update_seekdist(ad, aic, seek_dist); |
| } |
| aic->last_request_pos = rq->sector + rq->nr_sectors; |
| set_bit(AS_TASK_IOSTARTED, &aic->state); |
| spin_unlock(&aic->lock); |
| } |
| } |
| |
| /* |
| * as_close_req decides if one request is considered "close" to the |
| * previous one issued. |
| */ |
| static int as_close_req(struct as_data *ad, struct as_io_context *aic, |
| struct as_rq *arq) |
| { |
| unsigned long delay; /* milliseconds */ |
| sector_t last = ad->last_sector[ad->batch_data_dir]; |
| sector_t next = arq->request->sector; |
| sector_t delta; /* acceptable close offset (in sectors) */ |
| sector_t s; |
| |
| if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished) |
| delay = 0; |
| else |
| delay = ((jiffies - ad->antic_start) * 1000) / HZ; |
| |
| if (delay == 0) |
| delta = 8192; |
| else if (delay <= 20 && delay <= ad->antic_expire) |
| delta = 8192 << delay; |
| else |
| return 1; |
| |
| if ((last <= next + (delta>>1)) && (next <= last + delta)) |
| return 1; |
| |
| if (last < next) |
| s = next - last; |
| else |
| s = last - next; |
| |
| if (aic->seek_samples == 0) { |
| /* |
| * Process has just started IO. Use past statistics to |
| * gauge success possibility |
| */ |
| if (ad->new_seek_mean > s) { |
| /* this request is better than what we're expecting */ |
| return 1; |
| } |
| |
| } else { |
| if (aic->seek_mean > s) { |
| /* this request is better than what we're expecting */ |
| return 1; |
| } |
| } |
| |
| return 0; |
| } |
| |
| /* |
| * as_can_break_anticipation returns true if we have been anticipating this |
| * request. |
| * |
| * It also returns true if the process against which we are anticipating |
| * submits a write - that's presumably an fsync, O_SYNC write, etc. We want to |
| * dispatch it ASAP, because we know that application will not be submitting |
| * any new reads. |
| * |
| * If the task which has submitted the request has exited, break anticipation. |
| * |
| * If this task has queued some other IO, do not enter enticipation. |
| */ |
| static int as_can_break_anticipation(struct as_data *ad, struct as_rq *arq) |
| { |
| struct io_context *ioc; |
| struct as_io_context *aic; |
| |
| ioc = ad->io_context; |
| BUG_ON(!ioc); |
| |
| if (arq && ioc == arq->io_context) { |
| /* request from same process */ |
| return 1; |
| } |
| |
| if (ad->ioc_finished && as_antic_expired(ad)) { |
| /* |
| * In this situation status should really be FINISHED, |
| * however the timer hasn't had the chance to run yet. |
| */ |
| return 1; |
| } |
| |
| aic = ioc->aic; |
| if (!aic) |
| return 0; |
| |
| if (atomic_read(&aic->nr_queued) > 0) { |
| /* process has more requests queued */ |
| return 1; |
| } |
| |
| if (atomic_read(&aic->nr_dispatched) > 0) { |
| /* process has more requests dispatched */ |
| return 1; |
| } |
| |
| if (arq && arq->is_sync == REQ_SYNC && as_close_req(ad, aic, arq)) { |
| /* |
| * Found a close request that is not one of ours. |
| * |
| * This makes close requests from another process update |
| * our IO history. Is generally useful when there are |
| * two or more cooperating processes working in the same |
| * area. |
| */ |
| if (!test_bit(AS_TASK_RUNNING, &aic->state)) { |
| if (aic->ttime_samples == 0) |
| ad->exit_prob = (7*ad->exit_prob + 256)/8; |
| |
| ad->exit_no_coop = (7*ad->exit_no_coop)/8; |
| } |
| |
| as_update_iohist(ad, aic, arq->request); |
| return 1; |
| } |
| |
| if (!test_bit(AS_TASK_RUNNING, &aic->state)) { |
| /* process anticipated on has exited */ |
| if (aic->ttime_samples == 0) |
| ad->exit_prob = (7*ad->exit_prob + 256)/8; |
| |
| if (ad->exit_no_coop > 128) |
| return 1; |
| } |
| |
| if (aic->ttime_samples == 0) { |
| if (ad->new_ttime_mean > ad->antic_expire) |
| return 1; |
| if (ad->exit_prob * ad->exit_no_coop > 128*256) |
| return 1; |
| } else if (aic->ttime_mean > ad->antic_expire) { |
| /* the process thinks too much between requests */ |
| return 1; |
| } |
| |
| return 0; |
| } |
| |
| /* |
| * as_can_anticipate indicates weather we should either run arq |
| * or keep anticipating a better request. |
| */ |
| static int as_can_anticipate(struct as_data *ad, struct as_rq *arq) |
| { |
| if (!ad->io_context) |
| /* |
| * Last request submitted was a write |
| */ |
| return 0; |
| |
| if (ad->antic_status == ANTIC_FINISHED) |
| /* |
| * Don't restart if we have just finished. Run the next request |
| */ |
| return 0; |
| |
| if (as_can_break_anticipation(ad, arq)) |
| /* |
| * This request is a good candidate. Don't keep anticipating, |
| * run it. |
| */ |
| return 0; |
| |
| /* |
| * OK from here, we haven't finished, and don't have a decent request! |
| * Status is either ANTIC_OFF so start waiting, |
| * ANTIC_WAIT_REQ so continue waiting for request to finish |
| * or ANTIC_WAIT_NEXT so continue waiting for an acceptable request. |
| */ |
| |
| return 1; |
| } |
| |
| /* |
| * as_update_arq must be called whenever a request (arq) is added to |
| * the sort_list. This function keeps caches up to date, and checks if the |
| * request might be one we are "anticipating" |
| */ |
| static void as_update_arq(struct as_data *ad, struct as_rq *arq) |
| { |
| const int data_dir = arq->is_sync; |
| |
| /* keep the next_arq cache up to date */ |
| ad->next_arq[data_dir] = as_choose_req(ad, arq, ad->next_arq[data_dir]); |
| |
| /* |
| * have we been anticipating this request? |
| * or does it come from the same process as the one we are anticipating |
| * for? |
| */ |
| if (ad->antic_status == ANTIC_WAIT_REQ |
| || ad->antic_status == ANTIC_WAIT_NEXT) { |
| if (as_can_break_anticipation(ad, arq)) |
| as_antic_stop(ad); |
| } |
| } |
| |
| /* |
| * Gathers timings and resizes the write batch automatically |
| */ |
| static void update_write_batch(struct as_data *ad) |
| { |
| unsigned long batch = ad->batch_expire[REQ_ASYNC]; |
| long write_time; |
| |
| write_time = (jiffies - ad->current_batch_expires) + batch; |
| if (write_time < 0) |
| write_time = 0; |
| |
| if (write_time > batch && !ad->write_batch_idled) { |
| if (write_time > batch * 3) |
| ad->write_batch_count /= 2; |
| else |
| ad->write_batch_count--; |
| } else if (write_time < batch && ad->current_write_count == 0) { |
| if (batch > write_time * 3) |
| ad->write_batch_count *= 2; |
| else |
| ad->write_batch_count++; |
| } |
| |
| if (ad->write_batch_count < 1) |
| ad->write_batch_count = 1; |
| } |
| |
| /* |
| * as_completed_request is to be called when a request has completed and |
| * returned something to the requesting process, be it an error or data. |
| */ |
| static void as_completed_request(request_queue_t *q, struct request *rq) |
| { |
| struct as_data *ad = q->elevator->elevator_data; |
| struct as_rq *arq = RQ_DATA(rq); |
| |
| WARN_ON(!list_empty(&rq->queuelist)); |
| |
| if (arq->state != AS_RQ_REMOVED) { |
| printk("arq->state %d\n", arq->state); |
| WARN_ON(1); |
| goto out; |
| } |
| |
| if (ad->changed_batch && ad->nr_dispatched == 1) { |
| kblockd_schedule_work(&ad->antic_work); |
| ad->changed_batch = 0; |
| |
| if (ad->batch_data_dir == REQ_SYNC) |
| ad->new_batch = 1; |
| } |
| WARN_ON(ad->nr_dispatched == 0); |
| ad->nr_dispatched--; |
| |
| /* |
| * Start counting the batch from when a request of that direction is |
| * actually serviced. This should help devices with big TCQ windows |
| * and writeback caches |
| */ |
| if (ad->new_batch && ad->batch_data_dir == arq->is_sync) { |
| update_write_batch(ad); |
| ad->current_batch_expires = jiffies + |
| ad->batch_expire[REQ_SYNC]; |
| ad->new_batch = 0; |
| } |
| |
| if (ad->io_context == arq->io_context && ad->io_context) { |
| ad->antic_start = jiffies; |
| ad->ioc_finished = 1; |
| if (ad->antic_status == ANTIC_WAIT_REQ) { |
| /* |
| * We were waiting on this request, now anticipate |
| * the next one |
| */ |
| as_antic_waitnext(ad); |
| } |
| } |
| |
| as_put_io_context(arq); |
| out: |
| arq->state = AS_RQ_POSTSCHED; |
| } |
| |
| /* |
| * as_remove_queued_request removes a request from the pre dispatch queue |
| * without updating refcounts. It is expected the caller will drop the |
| * reference unless it replaces the request at somepart of the elevator |
| * (ie. the dispatch queue) |
| */ |
| static void as_remove_queued_request(request_queue_t *q, struct request *rq) |
| { |
| struct as_rq *arq = RQ_DATA(rq); |
| const int data_dir = arq->is_sync; |
| struct as_data *ad = q->elevator->elevator_data; |
| |
| WARN_ON(arq->state != AS_RQ_QUEUED); |
| |
| if (arq->io_context && arq->io_context->aic) { |
| BUG_ON(!atomic_read(&arq->io_context->aic->nr_queued)); |
| atomic_dec(&arq->io_context->aic->nr_queued); |
| } |
| |
| /* |
| * Update the "next_arq" cache if we are about to remove its |
| * entry |
| */ |
| if (ad->next_arq[data_dir] == arq) |
| ad->next_arq[data_dir] = as_find_next_arq(ad, arq); |
| |
| list_del_init(&arq->fifo); |
| as_del_arq_hash(arq); |
| as_del_arq_rb(ad, arq); |
| } |
| |
| /* |
| * as_fifo_expired returns 0 if there are no expired reads on the fifo, |
| * 1 otherwise. It is ratelimited so that we only perform the check once per |
| * `fifo_expire' interval. Otherwise a large number of expired requests |
| * would create a hopeless seekstorm. |
| * |
| * See as_antic_expired comment. |
| */ |
| static int as_fifo_expired(struct as_data *ad, int adir) |
| { |
| struct as_rq *arq; |
| long delta_jif; |
| |
| delta_jif = jiffies - ad->last_check_fifo[adir]; |
| if (unlikely(delta_jif < 0)) |
| delta_jif = -delta_jif; |
| if (delta_jif < ad->fifo_expire[adir]) |
| return 0; |
| |
| ad->last_check_fifo[adir] = jiffies; |
| |
| if (list_empty(&ad->fifo_list[adir])) |
| return 0; |
| |
| arq = list_entry_fifo(ad->fifo_list[adir].next); |
| |
| return time_after(jiffies, arq->expires); |
| } |
| |
| /* |
| * as_batch_expired returns true if the current batch has expired. A batch |
| * is a set of reads or a set of writes. |
| */ |
| static inline int as_batch_expired(struct as_data *ad) |
| { |
| if (ad->changed_batch || ad->new_batch) |
| return 0; |
| |
| if (ad->batch_data_dir == REQ_SYNC) |
| /* TODO! add a check so a complete fifo gets written? */ |
| return time_after(jiffies, ad->current_batch_expires); |
| |
| return time_after(jiffies, ad->current_batch_expires) |
| || ad->current_write_count == 0; |
| } |
| |
| /* |
| * move an entry to dispatch queue |
| */ |
| static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq) |
| { |
| struct request *rq = arq->request; |
| const int data_dir = arq->is_sync; |
| |
| BUG_ON(!ON_RB(&arq->rb_node)); |
| |
| as_antic_stop(ad); |
| ad->antic_status = ANTIC_OFF; |
| |
| /* |
| * This has to be set in order to be correctly updated by |
| * as_find_next_arq |
| */ |
| ad->last_sector[data_dir] = rq->sector + rq->nr_sectors; |
| |
| if (data_dir == REQ_SYNC) { |
| /* In case we have to anticipate after this */ |
| copy_io_context(&ad->io_context, &arq->io_context); |
| } else { |
| if (ad->io_context) { |
| put_io_context(ad->io_context); |
| ad->io_context = NULL; |
| } |
| |
| if (ad->current_write_count != 0) |
| ad->current_write_count--; |
| } |
| ad->ioc_finished = 0; |
| |
| ad->next_arq[data_dir] = as_find_next_arq(ad, arq); |
| |
| /* |
| * take it off the sort and fifo list, add to dispatch queue |
| */ |
| as_remove_queued_request(ad->q, rq); |
| WARN_ON(arq->state != AS_RQ_QUEUED); |
| |
| elv_dispatch_sort(ad->q, rq); |
| |
| arq->state = AS_RQ_DISPATCHED; |
| if (arq->io_context && arq->io_context->aic) |
| atomic_inc(&arq->io_context->aic->nr_dispatched); |
| ad->nr_dispatched++; |
| } |
| |
| /* |
| * as_dispatch_request selects the best request according to |
| * read/write expire, batch expire, etc, and moves it to the dispatch |
| * queue. Returns 1 if a request was found, 0 otherwise. |
| */ |
| static int as_dispatch_request(request_queue_t *q, int force) |
| { |
| struct as_data *ad = q->elevator->elevator_data; |
| struct as_rq *arq; |
| const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]); |
| const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]); |
| |
| if (unlikely(force)) { |
| /* |
| * Forced dispatch, accounting is useless. Reset |
| * accounting states and dump fifo_lists. Note that |
| * batch_data_dir is reset to REQ_SYNC to avoid |
| * screwing write batch accounting as write batch |
| * accounting occurs on W->R transition. |
| */ |
| int dispatched = 0; |
| |
| ad->batch_data_dir = REQ_SYNC; |
| ad->changed_batch = 0; |
| ad->new_batch = 0; |
| |
| while (ad->next_arq[REQ_SYNC]) { |
| as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]); |
| dispatched++; |
| } |
| ad->last_check_fifo[REQ_SYNC] = jiffies; |
| |
| while (ad->next_arq[REQ_ASYNC]) { |
| as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]); |
| dispatched++; |
| } |
| ad->last_check_fifo[REQ_ASYNC] = jiffies; |
| |
| return dispatched; |
| } |
| |
| /* Signal that the write batch was uncontended, so we can't time it */ |
| if (ad->batch_data_dir == REQ_ASYNC && !reads) { |
| if (ad->current_write_count == 0 || !writes) |
| ad->write_batch_idled = 1; |
| } |
| |
| if (!(reads || writes) |
| || ad->antic_status == ANTIC_WAIT_REQ |
| || ad->antic_status == ANTIC_WAIT_NEXT |
| || ad->changed_batch) |
| return 0; |
| |
| if (!(reads && writes && as_batch_expired(ad))) { |
| /* |
| * batch is still running or no reads or no writes |
| */ |
| arq = ad->next_arq[ad->batch_data_dir]; |
| |
| if (ad->batch_data_dir == REQ_SYNC && ad->antic_expire) { |
| if (as_fifo_expired(ad, REQ_SYNC)) |
| goto fifo_expired; |
| |
| if (as_can_anticipate(ad, arq)) { |
| as_antic_waitreq(ad); |
| return 0; |
| } |
| } |
| |
| if (arq) { |
| /* we have a "next request" */ |
| if (reads && !writes) |
| ad->current_batch_expires = |
| jiffies + ad->batch_expire[REQ_SYNC]; |
| goto dispatch_request; |
| } |
| } |
| |
| /* |
| * at this point we are not running a batch. select the appropriate |
| * data direction (read / write) |
| */ |
| |
| if (reads) { |
| BUG_ON(RB_EMPTY(&ad->sort_list[REQ_SYNC])); |
| |
| if (writes && ad->batch_data_dir == REQ_SYNC) |
| /* |
| * Last batch was a read, switch to writes |
| */ |
| goto dispatch_writes; |
| |
| if (ad->batch_data_dir == REQ_ASYNC) { |
| WARN_ON(ad->new_batch); |
| ad->changed_batch = 1; |
| } |
| ad->batch_data_dir = REQ_SYNC; |
| arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next); |
| ad->last_check_fifo[ad->batch_data_dir] = jiffies; |
| goto dispatch_request; |
| } |
| |
| /* |
| * the last batch was a read |
| */ |
| |
| if (writes) { |
| dispatch_writes: |
| BUG_ON(RB_EMPTY(&ad->sort_list[REQ_ASYNC])); |
| |
| if (ad->batch_data_dir == REQ_SYNC) { |
| ad->changed_batch = 1; |
| |
| /* |
| * new_batch might be 1 when the queue runs out of |
| * reads. A subsequent submission of a write might |
| * cause a change of batch before the read is finished. |
| */ |
| ad->new_batch = 0; |
| } |
| ad->batch_data_dir = REQ_ASYNC; |
| ad->current_write_count = ad->write_batch_count; |
| ad->write_batch_idled = 0; |
| arq = ad->next_arq[ad->batch_data_dir]; |
| goto dispatch_request; |
| } |
| |
| BUG(); |
| return 0; |
| |
| dispatch_request: |
| /* |
| * If a request has expired, service it. |
| */ |
| |
| if (as_fifo_expired(ad, ad->batch_data_dir)) { |
| fifo_expired: |
| arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next); |
| BUG_ON(arq == NULL); |
| } |
| |
| if (ad->changed_batch) { |
| WARN_ON(ad->new_batch); |
| |
| if (ad->nr_dispatched) |
| return 0; |
| |
| if (ad->batch_data_dir == REQ_ASYNC) |
| ad->current_batch_expires = jiffies + |
| ad->batch_expire[REQ_ASYNC]; |
| else |
| ad->new_batch = 1; |
| |
| ad->changed_batch = 0; |
| } |
| |
| /* |
| * arq is the selected appropriate request. |
| */ |
| as_move_to_dispatch(ad, arq); |
| |
| return 1; |
| } |
| |
| /* |
| * add arq to rbtree and fifo |
| */ |
| static void as_add_request(request_queue_t *q, struct request *rq) |
| { |
| struct as_data *ad = q->elevator->elevator_data; |
| struct as_rq *arq = RQ_DATA(rq); |
| int data_dir; |
| |
| arq->state = AS_RQ_NEW; |
| |
| if (rq_data_dir(arq->request) == READ |
| || current->flags&PF_SYNCWRITE) |
| arq->is_sync = 1; |
| else |
| arq->is_sync = 0; |
| data_dir = arq->is_sync; |
| |
| arq->io_context = as_get_io_context(); |
| |
| if (arq->io_context) { |
| as_update_iohist(ad, arq->io_context->aic, arq->request); |
| atomic_inc(&arq->io_context->aic->nr_queued); |
| } |
| |
| as_add_arq_rb(ad, arq); |
| if (rq_mergeable(arq->request)) |
| as_add_arq_hash(ad, arq); |
| |
| /* |
| * set expire time (only used for reads) and add to fifo list |
| */ |
| arq->expires = jiffies + ad->fifo_expire[data_dir]; |
| list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]); |
| |
| as_update_arq(ad, arq); /* keep state machine up to date */ |
| arq->state = AS_RQ_QUEUED; |
| } |
| |
| static void as_activate_request(request_queue_t *q, struct request *rq) |
| { |
| struct as_rq *arq = RQ_DATA(rq); |
| |
| WARN_ON(arq->state != AS_RQ_DISPATCHED); |
| arq->state = AS_RQ_REMOVED; |
| if (arq->io_context && arq->io_context->aic) |
| atomic_dec(&arq->io_context->aic->nr_dispatched); |
| } |
| |
| static void as_deactivate_request(request_queue_t *q, struct request *rq) |
| { |
| struct as_rq *arq = RQ_DATA(rq); |
| |
| WARN_ON(arq->state != AS_RQ_REMOVED); |
| arq->state = AS_RQ_DISPATCHED; |
| if (arq->io_context && arq->io_context->aic) |
| atomic_inc(&arq->io_context->aic->nr_dispatched); |
| } |
| |
| /* |
| * as_queue_empty tells us if there are requests left in the device. It may |
| * not be the case that a driver can get the next request even if the queue |
| * is not empty - it is used in the block layer to check for plugging and |
| * merging opportunities |
| */ |
| static int as_queue_empty(request_queue_t *q) |
| { |
| struct as_data *ad = q->elevator->elevator_data; |
| |
| return list_empty(&ad->fifo_list[REQ_ASYNC]) |
| && list_empty(&ad->fifo_list[REQ_SYNC]); |
| } |
| |
| static struct request *as_former_request(request_queue_t *q, |
| struct request *rq) |
| { |
| struct as_rq *arq = RQ_DATA(rq); |
| struct rb_node *rbprev = rb_prev(&arq->rb_node); |
| struct request *ret = NULL; |
| |
| if (rbprev) |
| ret = rb_entry_arq(rbprev)->request; |
| |
| return ret; |
| } |
| |
| static struct request *as_latter_request(request_queue_t *q, |
| struct request *rq) |
| { |
| struct as_rq *arq = RQ_DATA(rq); |
| struct rb_node *rbnext = rb_next(&arq->rb_node); |
| struct request *ret = NULL; |
| |
| if (rbnext) |
| ret = rb_entry_arq(rbnext)->request; |
| |
| return ret; |
| } |
| |
| static int |
| as_merge(request_queue_t *q, struct request **req, struct bio *bio) |
| { |
| struct as_data *ad = q->elevator->elevator_data; |
| sector_t rb_key = bio->bi_sector + bio_sectors(bio); |
| struct request *__rq; |
| int ret; |
| |
| /* |
| * see if the merge hash can satisfy a back merge |
| */ |
| __rq = as_find_arq_hash(ad, bio->bi_sector); |
| if (__rq) { |
| BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector); |
| |
| if (elv_rq_merge_ok(__rq, bio)) { |
| ret = ELEVATOR_BACK_MERGE; |
| goto out; |
| } |
| } |
| |
| /* |
| * check for front merge |
| */ |
| __rq = as_find_arq_rb(ad, rb_key, bio_data_dir(bio)); |
| if (__rq) { |
| BUG_ON(rb_key != rq_rb_key(__rq)); |
| |
| if (elv_rq_merge_ok(__rq, bio)) { |
| ret = ELEVATOR_FRONT_MERGE; |
| goto out; |
| } |
| } |
| |
| return ELEVATOR_NO_MERGE; |
| out: |
| if (ret) { |
| if (rq_mergeable(__rq)) |
| as_hot_arq_hash(ad, RQ_DATA(__rq)); |
| } |
| *req = __rq; |
| return ret; |
| } |
| |
| static void as_merged_request(request_queue_t *q, struct request *req) |
| { |
| struct as_data *ad = q->elevator->elevator_data; |
| struct as_rq *arq = RQ_DATA(req); |
| |
| /* |
| * hash always needs to be repositioned, key is end sector |
| */ |
| as_del_arq_hash(arq); |
| as_add_arq_hash(ad, arq); |
| |
| /* |
| * if the merge was a front merge, we need to reposition request |
| */ |
| if (rq_rb_key(req) != arq->rb_key) { |
| as_del_arq_rb(ad, arq); |
| as_add_arq_rb(ad, arq); |
| /* |
| * Note! At this stage of this and the next function, our next |
| * request may not be optimal - eg the request may have "grown" |
| * behind the disk head. We currently don't bother adjusting. |
| */ |
| } |
| } |
| |
| static void as_merged_requests(request_queue_t *q, struct request *req, |
| struct request *next) |
| { |
| struct as_data *ad = q->elevator->elevator_data; |
| struct as_rq *arq = RQ_DATA(req); |
| struct as_rq *anext = RQ_DATA(next); |
| |
| BUG_ON(!arq); |
| BUG_ON(!anext); |
| |
| /* |
| * reposition arq (this is the merged request) in hash, and in rbtree |
| * in case of a front merge |
| */ |
| as_del_arq_hash(arq); |
| as_add_arq_hash(ad, arq); |
| |
| if (rq_rb_key(req) != arq->rb_key) { |
| as_del_arq_rb(ad, arq); |
| as_add_arq_rb(ad, arq); |
| } |
| |
| /* |
| * if anext expires before arq, assign its expire time to arq |
| * and move into anext position (anext will be deleted) in fifo |
| */ |
| if (!list_empty(&arq->fifo) && !list_empty(&anext->fifo)) { |
| if (time_before(anext->expires, arq->expires)) { |
| list_move(&arq->fifo, &anext->fifo); |
| arq->expires = anext->expires; |
| /* |
| * Don't copy here but swap, because when anext is |
| * removed below, it must contain the unused context |
| */ |
| swap_io_context(&arq->io_context, &anext->io_context); |
| } |
| } |
| |
| /* |
| * kill knowledge of next, this one is a goner |
| */ |
| as_remove_queued_request(q, next); |
| as_put_io_context(anext); |
| |
| anext->state = AS_RQ_MERGED; |
| } |
| |
| /* |
| * This is executed in a "deferred" process context, by kblockd. It calls the |
| * driver's request_fn so the driver can submit that request. |
| * |
| * IMPORTANT! This guy will reenter the elevator, so set up all queue global |
| * state before calling, and don't rely on any state over calls. |
| * |
| * FIXME! dispatch queue is not a queue at all! |
| */ |
| static void as_work_handler(void *data) |
| { |
| struct request_queue *q = data; |
| unsigned long flags; |
| |
| spin_lock_irqsave(q->queue_lock, flags); |
| if (!as_queue_empty(q)) |
| q->request_fn(q); |
| spin_unlock_irqrestore(q->queue_lock, flags); |
| } |
| |
| static void as_put_request(request_queue_t *q, struct request *rq) |
| { |
| struct as_data *ad = q->elevator->elevator_data; |
| struct as_rq *arq = RQ_DATA(rq); |
| |
| if (!arq) { |
| WARN_ON(1); |
| return; |
| } |
| |
| if (unlikely(arq->state != AS_RQ_POSTSCHED && |
| arq->state != AS_RQ_PRESCHED && |
| arq->state != AS_RQ_MERGED)) { |
| printk("arq->state %d\n", arq->state); |
| WARN_ON(1); |
| } |
| |
| mempool_free(arq, ad->arq_pool); |
| rq->elevator_private = NULL; |
| } |
| |
| static int as_set_request(request_queue_t *q, struct request *rq, |
| struct bio *bio, gfp_t gfp_mask) |
| { |
| struct as_data *ad = q->elevator->elevator_data; |
| struct as_rq *arq = mempool_alloc(ad->arq_pool, gfp_mask); |
| |
| if (arq) { |
| memset(arq, 0, sizeof(*arq)); |
| RB_CLEAR(&arq->rb_node); |
| arq->request = rq; |
| arq->state = AS_RQ_PRESCHED; |
| arq->io_context = NULL; |
| INIT_LIST_HEAD(&arq->hash); |
| arq->on_hash = 0; |
| INIT_LIST_HEAD(&arq->fifo); |
| rq->elevator_private = arq; |
| return 0; |
| } |
| |
| return 1; |
| } |
| |
| static int as_may_queue(request_queue_t *q, int rw, struct bio *bio) |
| { |
| int ret = ELV_MQUEUE_MAY; |
| struct as_data *ad = q->elevator->elevator_data; |
| struct io_context *ioc; |
| if (ad->antic_status == ANTIC_WAIT_REQ || |
| ad->antic_status == ANTIC_WAIT_NEXT) { |
| ioc = as_get_io_context(); |
| if (ad->io_context == ioc) |
| ret = ELV_MQUEUE_MUST; |
| put_io_context(ioc); |
| } |
| |
| return ret; |
| } |
| |
| static void as_exit_queue(elevator_t *e) |
| { |
| struct as_data *ad = e->elevator_data; |
| |
| del_timer_sync(&ad->antic_timer); |
| kblockd_flush(); |
| |
| BUG_ON(!list_empty(&ad->fifo_list[REQ_SYNC])); |
| BUG_ON(!list_empty(&ad->fifo_list[REQ_ASYNC])); |
| |
| mempool_destroy(ad->arq_pool); |
| put_io_context(ad->io_context); |
| kfree(ad->hash); |
| kfree(ad); |
| } |
| |
| /* |
| * initialize elevator private data (as_data), and alloc a arq for |
| * each request on the free lists |
| */ |
| static int as_init_queue(request_queue_t *q, elevator_t *e) |
| { |
| struct as_data *ad; |
| int i; |
| |
| if (!arq_pool) |
| return -ENOMEM; |
| |
| ad = kmalloc_node(sizeof(*ad), GFP_KERNEL, q->node); |
| if (!ad) |
| return -ENOMEM; |
| memset(ad, 0, sizeof(*ad)); |
| |
| ad->q = q; /* Identify what queue the data belongs to */ |
| |
| ad->hash = kmalloc_node(sizeof(struct list_head)*AS_HASH_ENTRIES, |
| GFP_KERNEL, q->node); |
| if (!ad->hash) { |
| kfree(ad); |
| return -ENOMEM; |
| } |
| |
| ad->arq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab, |
| mempool_free_slab, arq_pool, q->node); |
| if (!ad->arq_pool) { |
| kfree(ad->hash); |
| kfree(ad); |
| return -ENOMEM; |
| } |
| |
| /* anticipatory scheduling helpers */ |
| ad->antic_timer.function = as_antic_timeout; |
| ad->antic_timer.data = (unsigned long)q; |
| init_timer(&ad->antic_timer); |
| INIT_WORK(&ad->antic_work, as_work_handler, q); |
| |
| for (i = 0; i < AS_HASH_ENTRIES; i++) |
| INIT_LIST_HEAD(&ad->hash[i]); |
| |
| INIT_LIST_HEAD(&ad->fifo_list[REQ_SYNC]); |
| INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]); |
| ad->sort_list[REQ_SYNC] = RB_ROOT; |
| ad->sort_list[REQ_ASYNC] = RB_ROOT; |
| ad->fifo_expire[REQ_SYNC] = default_read_expire; |
| ad->fifo_expire[REQ_ASYNC] = default_write_expire; |
| ad->antic_expire = default_antic_expire; |
| ad->batch_expire[REQ_SYNC] = default_read_batch_expire; |
| ad->batch_expire[REQ_ASYNC] = default_write_batch_expire; |
| e->elevator_data = ad; |
| |
| ad->current_batch_expires = jiffies + ad->batch_expire[REQ_SYNC]; |
| ad->write_batch_count = ad->batch_expire[REQ_ASYNC] / 10; |
| if (ad->write_batch_count < 2) |
| ad->write_batch_count = 2; |
| |
| return 0; |
| } |
| |
| /* |
| * sysfs parts below |
| */ |
| |
| static ssize_t |
| as_var_show(unsigned int var, char *page) |
| { |
| return sprintf(page, "%d\n", var); |
| } |
| |
| static ssize_t |
| as_var_store(unsigned long *var, const char *page, size_t count) |
| { |
| char *p = (char *) page; |
| |
| *var = simple_strtoul(p, &p, 10); |
| return count; |
| } |
| |
| static ssize_t est_time_show(elevator_t *e, char *page) |
| { |
| struct as_data *ad = e->elevator_data; |
| int pos = 0; |
| |
| pos += sprintf(page+pos, "%lu %% exit probability\n", |
| 100*ad->exit_prob/256); |
| pos += sprintf(page+pos, "%lu %% probability of exiting without a " |
| "cooperating process submitting IO\n", |
| 100*ad->exit_no_coop/256); |
| pos += sprintf(page+pos, "%lu ms new thinktime\n", ad->new_ttime_mean); |
| pos += sprintf(page+pos, "%llu sectors new seek distance\n", |
| (unsigned long long)ad->new_seek_mean); |
| |
| return pos; |
| } |
| |
| #define SHOW_FUNCTION(__FUNC, __VAR) \ |
| static ssize_t __FUNC(elevator_t *e, char *page) \ |
| { \ |
| struct as_data *ad = e->elevator_data; \ |
| return as_var_show(jiffies_to_msecs((__VAR)), (page)); \ |
| } |
| SHOW_FUNCTION(as_read_expire_show, ad->fifo_expire[REQ_SYNC]); |
| SHOW_FUNCTION(as_write_expire_show, ad->fifo_expire[REQ_ASYNC]); |
| SHOW_FUNCTION(as_antic_expire_show, ad->antic_expire); |
| SHOW_FUNCTION(as_read_batch_expire_show, ad->batch_expire[REQ_SYNC]); |
| SHOW_FUNCTION(as_write_batch_expire_show, ad->batch_expire[REQ_ASYNC]); |
| #undef SHOW_FUNCTION |
| |
| #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \ |
| static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \ |
| { \ |
| struct as_data *ad = e->elevator_data; \ |
| int ret = as_var_store(__PTR, (page), count); \ |
| if (*(__PTR) < (MIN)) \ |
| *(__PTR) = (MIN); \ |
| else if (*(__PTR) > (MAX)) \ |
| *(__PTR) = (MAX); \ |
| *(__PTR) = msecs_to_jiffies(*(__PTR)); \ |
| return ret; \ |
| } |
| STORE_FUNCTION(as_read_expire_store, &ad->fifo_expire[REQ_SYNC], 0, INT_MAX); |
| STORE_FUNCTION(as_write_expire_store, &ad->fifo_expire[REQ_ASYNC], 0, INT_MAX); |
| STORE_FUNCTION(as_antic_expire_store, &ad->antic_expire, 0, INT_MAX); |
| STORE_FUNCTION(as_read_batch_expire_store, |
| &ad->batch_expire[REQ_SYNC], 0, INT_MAX); |
| STORE_FUNCTION(as_write_batch_expire_store, |
| &ad->batch_expire[REQ_ASYNC], 0, INT_MAX); |
| #undef STORE_FUNCTION |
| |
| #define AS_ATTR(name) \ |
| __ATTR(name, S_IRUGO|S_IWUSR, as_##name##_show, as_##name##_store) |
| |
| static struct elv_fs_entry as_attrs[] = { |
| __ATTR_RO(est_time), |
| AS_ATTR(read_expire), |
| AS_ATTR(write_expire), |
| AS_ATTR(antic_expire), |
| AS_ATTR(read_batch_expire), |
| AS_ATTR(write_batch_expire), |
| __ATTR_NULL |
| }; |
| |
| static struct elevator_type iosched_as = { |
| .ops = { |
| .elevator_merge_fn = as_merge, |
| .elevator_merged_fn = as_merged_request, |
| .elevator_merge_req_fn = as_merged_requests, |
| .elevator_dispatch_fn = as_dispatch_request, |
| .elevator_add_req_fn = as_add_request, |
| .elevator_activate_req_fn = as_activate_request, |
| .elevator_deactivate_req_fn = as_deactivate_request, |
| .elevator_queue_empty_fn = as_queue_empty, |
| .elevator_completed_req_fn = as_completed_request, |
| .elevator_former_req_fn = as_former_request, |
| .elevator_latter_req_fn = as_latter_request, |
| .elevator_set_req_fn = as_set_request, |
| .elevator_put_req_fn = as_put_request, |
| .elevator_may_queue_fn = as_may_queue, |
| .elevator_init_fn = as_init_queue, |
| .elevator_exit_fn = as_exit_queue, |
| .trim = as_trim, |
| }, |
| |
| .elevator_attrs = as_attrs, |
| .elevator_name = "anticipatory", |
| .elevator_owner = THIS_MODULE, |
| }; |
| |
| static int __init as_init(void) |
| { |
| int ret; |
| |
| arq_pool = kmem_cache_create("as_arq", sizeof(struct as_rq), |
| 0, 0, NULL, NULL); |
| if (!arq_pool) |
| return -ENOMEM; |
| |
| ret = elv_register(&iosched_as); |
| if (!ret) { |
| /* |
| * don't allow AS to get unregistered, since we would have |
| * to browse all tasks in the system and release their |
| * as_io_context first |
| */ |
| __module_get(THIS_MODULE); |
| return 0; |
| } |
| |
| kmem_cache_destroy(arq_pool); |
| return ret; |
| } |
| |
| static void __exit as_exit(void) |
| { |
| DECLARE_COMPLETION(all_gone); |
| elv_unregister(&iosched_as); |
| ioc_gone = &all_gone; |
| /* ioc_gone's update must be visible before reading ioc_count */ |
| smp_wmb(); |
| if (atomic_read(&ioc_count)) |
| wait_for_completion(ioc_gone); |
| synchronize_rcu(); |
| kmem_cache_destroy(arq_pool); |
| } |
| |
| module_init(as_init); |
| module_exit(as_exit); |
| |
| MODULE_AUTHOR("Nick Piggin"); |
| MODULE_LICENSE("GPL"); |
| MODULE_DESCRIPTION("anticipatory IO scheduler"); |