/* * 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 */ #include #include #include #include #include #include #include /* * tunables */ static const int cfq_quantum = 4; /* max queue in one round of service */ static const int cfq_queued = 8; /* minimum rq allocate limit per-queue*/ static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 }; static const int cfq_back_max = 16 * 1024; /* maximum backwards seek, in KiB */ static const int cfq_back_penalty = 2; /* penalty of a backwards seek */ static const int cfq_slice_sync = HZ / 10; static int cfq_slice_async = HZ / 25; static const int cfq_slice_async_rq = 2; static int cfq_slice_idle = HZ / 70; #define CFQ_IDLE_GRACE (HZ / 10) #define CFQ_SLICE_SCALE (5) #define CFQ_KEY_ASYNC (0) static DEFINE_RWLOCK(cfq_exit_lock); /* * for the hash of cfqq inside the cfqd */ #define CFQ_QHASH_SHIFT 6 #define CFQ_QHASH_ENTRIES (1 << CFQ_QHASH_SHIFT) #define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash) /* * for the hash of crq inside the cfqq */ #define CFQ_MHASH_SHIFT 6 #define CFQ_MHASH_BLOCK(sec) ((sec) >> 3) #define CFQ_MHASH_ENTRIES (1 << CFQ_MHASH_SHIFT) #define CFQ_MHASH_FN(sec) hash_long(CFQ_MHASH_BLOCK(sec), CFQ_MHASH_SHIFT) #define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors) #define list_entry_hash(ptr) hlist_entry((ptr), struct cfq_rq, hash) #define list_entry_cfqq(ptr) list_entry((ptr), struct cfq_queue, cfq_list) #define list_entry_fifo(ptr) list_entry((ptr), struct request, queuelist) #define RQ_DATA(rq) (rq)->elevator_private /* * rb-tree defines */ #define RB_NONE (2) #define RB_EMPTY(node) ((node)->rb_node == NULL) #define RB_CLEAR_COLOR(node) (node)->rb_color = RB_NONE #define RB_CLEAR(node) do { \ (node)->rb_parent = NULL; \ RB_CLEAR_COLOR((node)); \ (node)->rb_right = NULL; \ (node)->rb_left = NULL; \ } while (0) #define RB_CLEAR_ROOT(root) ((root)->rb_node = NULL) #define rb_entry_crq(node) rb_entry((node), struct cfq_rq, rb_node) #define rq_rb_key(rq) (rq)->sector static kmem_cache_t *crq_pool; static kmem_cache_t *cfq_pool; static kmem_cache_t *cfq_ioc_pool; static atomic_t ioc_count = ATOMIC_INIT(0); static struct completion *ioc_gone; #define CFQ_PRIO_LISTS IOPRIO_BE_NR #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE) #define cfq_class_be(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_BE) #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT) #define ASYNC (0) #define SYNC (1) #define cfq_cfqq_dispatched(cfqq) \ ((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC]) #define cfq_cfqq_class_sync(cfqq) ((cfqq)->key != CFQ_KEY_ASYNC) #define cfq_cfqq_sync(cfqq) \ (cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC]) #define sample_valid(samples) ((samples) > 80) /* * Per block device queue structure */ struct cfq_data { request_queue_t *queue; /* * rr list of queues with requests and the count of them */ struct list_head rr_list[CFQ_PRIO_LISTS]; struct list_head busy_rr; struct list_head cur_rr; struct list_head idle_rr; unsigned int busy_queues; /* * non-ordered list of empty cfqq's */ struct list_head empty_list; /* * cfqq lookup hash */ struct hlist_head *cfq_hash; /* * global crq hash for all queues */ struct hlist_head *crq_hash; unsigned int max_queued; mempool_t *crq_pool; int rq_in_driver; /* * schedule slice state info */ /* * idle window management */ struct timer_list idle_slice_timer; struct work_struct unplug_work; struct cfq_queue *active_queue; struct cfq_io_context *active_cic; int cur_prio, cur_end_prio; unsigned int dispatch_slice; struct timer_list idle_class_timer; sector_t last_sector; unsigned long last_end_request; unsigned int rq_starved; /* * tunables, see top of file */ unsigned int cfq_quantum; unsigned int cfq_queued; unsigned int cfq_fifo_expire[2]; unsigned int cfq_back_penalty; unsigned int cfq_back_max; unsigned int cfq_slice[2]; unsigned int cfq_slice_async_rq; unsigned int cfq_slice_idle; struct list_head cic_list; }; /* * Per process-grouping structure */ struct cfq_queue { /* reference count */ atomic_t ref; /* parent cfq_data */ struct cfq_data *cfqd; /* cfqq lookup hash */ struct hlist_node cfq_hash; /* hash key */ unsigned int key; /* on either rr or empty list of cfqd */ struct list_head cfq_list; /* sorted list of pending requests */ struct rb_root sort_list; /* if fifo isn't expired, next request to serve */ struct cfq_rq *next_crq; /* requests queued in sort_list */ int queued[2]; /* currently allocated requests */ int allocated[2]; /* fifo list of requests in sort_list */ struct list_head fifo; unsigned long slice_start; unsigned long slice_end; unsigned long slice_left; unsigned long service_last; /* number of requests that are on the dispatch list */ int on_dispatch[2]; /* io prio of this group */ unsigned short ioprio, org_ioprio; unsigned short ioprio_class, org_ioprio_class; /* various state flags, see below */ unsigned int flags; }; struct cfq_rq { struct rb_node rb_node; sector_t rb_key; struct request *request; struct hlist_node hash; struct cfq_queue *cfq_queue; struct cfq_io_context *io_context; unsigned int crq_flags; }; enum cfqq_state_flags { CFQ_CFQQ_FLAG_on_rr = 0, CFQ_CFQQ_FLAG_wait_request, CFQ_CFQQ_FLAG_must_alloc, CFQ_CFQQ_FLAG_must_alloc_slice, CFQ_CFQQ_FLAG_must_dispatch, CFQ_CFQQ_FLAG_fifo_expire, CFQ_CFQQ_FLAG_idle_window, CFQ_CFQQ_FLAG_prio_changed, }; #define CFQ_CFQQ_FNS(name) \ static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \ { \ cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \ } \ static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \ { \ cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \ } \ static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \ { \ return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \ } CFQ_CFQQ_FNS(on_rr); CFQ_CFQQ_FNS(wait_request); CFQ_CFQQ_FNS(must_alloc); CFQ_CFQQ_FNS(must_alloc_slice); CFQ_CFQQ_FNS(must_dispatch); CFQ_CFQQ_FNS(fifo_expire); CFQ_CFQQ_FNS(idle_window); CFQ_CFQQ_FNS(prio_changed); #undef CFQ_CFQQ_FNS enum cfq_rq_state_flags { CFQ_CRQ_FLAG_is_sync = 0, }; #define CFQ_CRQ_FNS(name) \ static inline void cfq_mark_crq_##name(struct cfq_rq *crq) \ { \ crq->crq_flags |= (1 << CFQ_CRQ_FLAG_##name); \ } \ static inline void cfq_clear_crq_##name(struct cfq_rq *crq) \ { \ crq->crq_flags &= ~(1 << CFQ_CRQ_FLAG_##name); \ } \ static inline int cfq_crq_##name(const struct cfq_rq *crq) \ { \ return (crq->crq_flags & (1 << CFQ_CRQ_FLAG_##name)) != 0; \ } CFQ_CRQ_FNS(is_sync); #undef CFQ_CRQ_FNS static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short); static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *); static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask); #define process_sync(tsk) ((tsk)->flags & PF_SYNCWRITE) /* * lots of deadline iosched dupes, can be abstracted later... */ static inline void cfq_del_crq_hash(struct cfq_rq *crq) { hlist_del_init(&crq->hash); } static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq) { const int hash_idx = CFQ_MHASH_FN(rq_hash_key(crq->request)); hlist_add_head(&crq->hash, &cfqd->crq_hash[hash_idx]); } static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset) { struct hlist_head *hash_list = &cfqd->crq_hash[CFQ_MHASH_FN(offset)]; struct hlist_node *entry, *next; hlist_for_each_safe(entry, next, hash_list) { struct cfq_rq *crq = list_entry_hash(entry); struct request *__rq = crq->request; if (!rq_mergeable(__rq)) { cfq_del_crq_hash(crq); continue; } if (rq_hash_key(__rq) == offset) return __rq; } return NULL; } /* * scheduler run of queue, if there are requests pending and no one in the * driver that will restart queueing */ static inline void cfq_schedule_dispatch(struct cfq_data *cfqd) { if (cfqd->busy_queues) kblockd_schedule_work(&cfqd->unplug_work); } static int cfq_queue_empty(request_queue_t *q) { struct cfq_data *cfqd = q->elevator->elevator_data; return !cfqd->busy_queues; } static inline pid_t cfq_queue_pid(struct task_struct *task, int rw) { if (rw == READ || process_sync(task)) return task->pid; return CFQ_KEY_ASYNC; } /* * Lifted from AS - choose which of crq1 and crq2 that is best served now. * We choose the request that is closest to the head right now. Distance * behind the head is penalized and only allowed to a certain extent. */ static struct cfq_rq * cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2) { sector_t last, s1, s2, d1 = 0, d2 = 0; unsigned long back_max; #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */ #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */ unsigned wrap = 0; /* bit mask: requests behind the disk head? */ if (crq1 == NULL || crq1 == crq2) return crq2; if (crq2 == NULL) return crq1; if (cfq_crq_is_sync(crq1) && !cfq_crq_is_sync(crq2)) return crq1; else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1)) return crq2; s1 = crq1->request->sector; s2 = crq2->request->sector; last = cfqd->last_sector; /* * by definition, 1KiB is 2 sectors */ back_max = cfqd->cfq_back_max * 2; /* * Strict one way elevator _except_ in the case where we allow * short backward seeks which are biased as twice the cost of a * similar forward seek. */ if (s1 >= last) d1 = s1 - last; else if (s1 + back_max >= last) d1 = (last - s1) * cfqd->cfq_back_penalty; else wrap |= CFQ_RQ1_WRAP; if (s2 >= last) d2 = s2 - last; else if (s2 + back_max >= last) d2 = (last - s2) * cfqd->cfq_back_penalty; else wrap |= CFQ_RQ2_WRAP; /* Found required data */ /* * By doing switch() on the bit mask "wrap" we avoid having to * check two variables for all permutations: --> faster! */ switch (wrap) { case 0: /* common case for CFQ: crq1 and crq2 not wrapped */ if (d1 < d2) return crq1; else if (d2 < d1) return crq2; else { if (s1 >= s2) return crq1; else return crq2; } case CFQ_RQ2_WRAP: return crq1; case CFQ_RQ1_WRAP: return crq2; case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both crqs wrapped */ default: /* * Since both rqs are wrapped, * start with the one that's further behind head * (--> only *one* back seek required), * since back seek takes more time than forward. */ if (s1 <= s2) return crq1; else return crq2; } } /* * would be nice to take fifo expire time into account as well */ static struct cfq_rq * cfq_find_next_crq(struct cfq_data *cfqd, struct cfq_queue *cfqq, struct cfq_rq *last) { struct cfq_rq *crq_next = NULL, *crq_prev = NULL; struct rb_node *rbnext, *rbprev; if (!(rbnext = rb_next(&last->rb_node))) { rbnext = rb_first(&cfqq->sort_list); if (rbnext == &last->rb_node) rbnext = NULL; } rbprev = rb_prev(&last->rb_node); if (rbprev) crq_prev = rb_entry_crq(rbprev); if (rbnext) crq_next = rb_entry_crq(rbnext); return cfq_choose_req(cfqd, crq_next, crq_prev); } static void cfq_update_next_crq(struct cfq_rq *crq) { struct cfq_queue *cfqq = crq->cfq_queue; if (cfqq->next_crq == crq) cfqq->next_crq = cfq_find_next_crq(cfqq->cfqd, cfqq, crq); } static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted) { struct cfq_data *cfqd = cfqq->cfqd; struct list_head *list, *entry; BUG_ON(!cfq_cfqq_on_rr(cfqq)); list_del(&cfqq->cfq_list); if (cfq_class_rt(cfqq)) list = &cfqd->cur_rr; else if (cfq_class_idle(cfqq)) list = &cfqd->idle_rr; else { /* * if cfqq has requests in flight, don't allow it to be * found in cfq_set_active_queue before it has finished them. * this is done to increase fairness between a process that * has lots of io pending vs one that only generates one * sporadically or synchronously */ if (cfq_cfqq_dispatched(cfqq)) list = &cfqd->busy_rr; else list = &cfqd->rr_list[cfqq->ioprio]; } /* * if queue was preempted, just add to front to be fair. busy_rr * isn't sorted. */ if (preempted || list == &cfqd->busy_rr) { list_add(&cfqq->cfq_list, list); return; } /* * sort by when queue was last serviced */ entry = list; while ((entry = entry->prev) != list) { struct cfq_queue *__cfqq = list_entry_cfqq(entry); if (!__cfqq->service_last) break; if (time_before(__cfqq->service_last, cfqq->service_last)) break; } list_add(&cfqq->cfq_list, entry); } /* * add to busy list of queues for service, trying to be fair in ordering * the pending list according to last request service */ static inline void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) { BUG_ON(cfq_cfqq_on_rr(cfqq)); cfq_mark_cfqq_on_rr(cfqq); cfqd->busy_queues++; cfq_resort_rr_list(cfqq, 0); } static inline void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) { BUG_ON(!cfq_cfqq_on_rr(cfqq)); cfq_clear_cfqq_on_rr(cfqq); list_move(&cfqq->cfq_list, &cfqd->empty_list); BUG_ON(!cfqd->busy_queues); cfqd->busy_queues--; } /* * rb tree support functions */ static inline void cfq_del_crq_rb(struct cfq_rq *crq) { struct cfq_queue *cfqq = crq->cfq_queue; struct cfq_data *cfqd = cfqq->cfqd; const int sync = cfq_crq_is_sync(crq); BUG_ON(!cfqq->queued[sync]); cfqq->queued[sync]--; cfq_update_next_crq(crq); rb_erase(&crq->rb_node, &cfqq->sort_list); RB_CLEAR_COLOR(&crq->rb_node); if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY(&cfqq->sort_list)) cfq_del_cfqq_rr(cfqd, cfqq); } static struct cfq_rq * __cfq_add_crq_rb(struct cfq_rq *crq) { struct rb_node **p = &crq->cfq_queue->sort_list.rb_node; struct rb_node *parent = NULL; struct cfq_rq *__crq; while (*p) { parent = *p; __crq = rb_entry_crq(parent); if (crq->rb_key < __crq->rb_key) p = &(*p)->rb_left; else if (crq->rb_key > __crq->rb_key) p = &(*p)->rb_right; else return __crq; } rb_link_node(&crq->rb_node, parent, p); return NULL; } static void cfq_add_crq_rb(struct cfq_rq *crq) { struct cfq_queue *cfqq = crq->cfq_queue; struct cfq_data *cfqd = cfqq->cfqd; struct request *rq = crq->request; struct cfq_rq *__alias; crq->rb_key = rq_rb_key(rq); cfqq->queued[cfq_crq_is_sync(crq)]++; /* * looks a little odd, but the first insert might return an alias. * if that happens, put the alias on the dispatch list */ while ((__alias = __cfq_add_crq_rb(crq)) != NULL) cfq_dispatch_insert(cfqd->queue, __alias); rb_insert_color(&crq->rb_node, &cfqq->sort_list); if (!cfq_cfqq_on_rr(cfqq)) cfq_add_cfqq_rr(cfqd, cfqq); /* * check if this request is a better next-serve candidate */ cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq); } static inline void cfq_reposition_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq) { rb_erase(&crq->rb_node, &cfqq->sort_list); cfqq->queued[cfq_crq_is_sync(crq)]--; cfq_add_crq_rb(crq); } static struct request * cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio) { struct task_struct *tsk = current; pid_t key = cfq_queue_pid(tsk, bio_data_dir(bio)); struct cfq_queue *cfqq; struct rb_node *n; sector_t sector; cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio); if (!cfqq) goto out; sector = bio->bi_sector + bio_sectors(bio); n = cfqq->sort_list.rb_node; while (n) { struct cfq_rq *crq = rb_entry_crq(n); if (sector < crq->rb_key) n = n->rb_left; else if (sector > crq->rb_key) n = n->rb_right; else return crq->request; } out: return NULL; } static void cfq_activate_request(request_queue_t *q, struct request *rq) { struct cfq_data *cfqd = q->elevator->elevator_data; cfqd->rq_in_driver++; } static void cfq_deactivate_request(request_queue_t *q, struct request *rq) { struct cfq_data *cfqd = q->elevator->elevator_data; WARN_ON(!cfqd->rq_in_driver); cfqd->rq_in_driver--; } static void cfq_remove_request(struct request *rq) { struct cfq_rq *crq = RQ_DATA(rq); list_del_init(&rq->queuelist); cfq_del_crq_rb(crq); cfq_del_crq_hash(crq); } static int cfq_merge(request_queue_t *q, struct request **req, struct bio *bio) { struct cfq_data *cfqd = q->elevator->elevator_data; struct request *__rq; int ret; __rq = cfq_find_rq_hash(cfqd, bio->bi_sector); if (__rq && elv_rq_merge_ok(__rq, bio)) { ret = ELEVATOR_BACK_MERGE; goto out; } __rq = cfq_find_rq_fmerge(cfqd, bio); if (__rq && elv_rq_merge_ok(__rq, bio)) { ret = ELEVATOR_FRONT_MERGE; goto out; } return ELEVATOR_NO_MERGE; out: *req = __rq; return ret; } static void cfq_merged_request(request_queue_t *q, struct request *req) { struct cfq_data *cfqd = q->elevator->elevator_data; struct cfq_rq *crq = RQ_DATA(req); cfq_del_crq_hash(crq); cfq_add_crq_hash(cfqd, crq); if (rq_rb_key(req) != crq->rb_key) { struct cfq_queue *cfqq = crq->cfq_queue; cfq_update_next_crq(crq); cfq_reposition_crq_rb(cfqq, crq); } } static void cfq_merged_requests(request_queue_t *q, struct request *rq, struct request *next) { cfq_merged_request(q, rq); /* * reposition in fifo if next is older than rq */ if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && time_before(next->start_time, rq->start_time)) list_move(&rq->queuelist, &next->queuelist); cfq_remove_request(next); } static inline void __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) { if (cfqq) { /* * stop potential idle class queues waiting service */ del_timer(&cfqd->idle_class_timer); cfqq->slice_start = jiffies; cfqq->slice_end = 0; cfqq->slice_left = 0; cfq_clear_cfqq_must_alloc_slice(cfqq); cfq_clear_cfqq_fifo_expire(cfqq); } cfqd->active_queue = cfqq; } /* * current cfqq expired its slice (or was too idle), select new one */ static void __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, int preempted) { unsigned long now = jiffies; if (cfq_cfqq_wait_request(cfqq)) del_timer(&cfqd->idle_slice_timer); if (!preempted && !cfq_cfqq_dispatched(cfqq)) { cfqq->service_last = now; cfq_schedule_dispatch(cfqd); } cfq_clear_cfqq_must_dispatch(cfqq); cfq_clear_cfqq_wait_request(cfqq); /* * store what was left of this slice, if the queue idled out * or was preempted */ if (time_after(cfqq->slice_end, now)) cfqq->slice_left = cfqq->slice_end - now; else cfqq->slice_left = 0; if (cfq_cfqq_on_rr(cfqq)) cfq_resort_rr_list(cfqq, preempted); if (cfqq == cfqd->active_queue) cfqd->active_queue = NULL; if (cfqd->active_cic) { put_io_context(cfqd->active_cic->ioc); cfqd->active_cic = NULL; } cfqd->dispatch_slice = 0; } static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted) { struct cfq_queue *cfqq = cfqd->active_queue; if (cfqq) __cfq_slice_expired(cfqd, cfqq, preempted); } /* * 0 * 0,1 * 0,1,2 * 0,1,2,3 * 0,1,2,3,4 * 0,1,2,3,4,5 * 0,1,2,3,4,5,6 * 0,1,2,3,4,5,6,7 */ static int cfq_get_next_prio_level(struct cfq_data *cfqd) { int prio, wrap; prio = -1; wrap = 0; do { int p; for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) { if (!list_empty(&cfqd->rr_list[p])) { prio = p; break; } } if (prio != -1) break; cfqd->cur_prio = 0; if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) { cfqd->cur_end_prio = 0; if (wrap) break; wrap = 1; } } while (1); if (unlikely(prio == -1)) return -1; BUG_ON(prio >= CFQ_PRIO_LISTS); list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr); cfqd->cur_prio = prio + 1; if (cfqd->cur_prio > cfqd->cur_end_prio) { cfqd->cur_end_prio = cfqd->cur_prio; cfqd->cur_prio = 0; } if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) { cfqd->cur_prio = 0; cfqd->cur_end_prio = 0; } return prio; } static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd) { struct cfq_queue *cfqq = NULL; /* * if current list is non-empty, grab first entry. if it is empty, * get next prio level and grab first entry then if any are spliced */ if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1) cfqq = list_entry_cfqq(cfqd->cur_rr.next); /* * if we have idle queues and no rt or be queues had pending * requests, either allow immediate service if the grace period * has passed or arm the idle grace timer */ if (!cfqq && !list_empty(&cfqd->idle_rr)) { unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE; if (time_after_eq(jiffies, end)) cfqq = list_entry_cfqq(cfqd->idle_rr.next); else mod_timer(&cfqd->idle_class_timer, end); } __cfq_set_active_queue(cfqd, cfqq); return cfqq; } static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq) { struct cfq_io_context *cic; unsigned long sl; WARN_ON(!RB_EMPTY(&cfqq->sort_list)); WARN_ON(cfqq != cfqd->active_queue); /* * idle is disabled, either manually or by past process history */ if (!cfqd->cfq_slice_idle) return 0; if (!cfq_cfqq_idle_window(cfqq)) return 0; /* * task has exited, don't wait */ cic = cfqd->active_cic; if (!cic || !cic->ioc->task) return 0; cfq_mark_cfqq_must_dispatch(cfqq); cfq_mark_cfqq_wait_request(cfqq); sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle); /* * we don't want to idle for seeks, but we do want to allow * fair distribution of slice time for a process doing back-to-back * seeks. so allow a little bit of time for him to submit a new rq */ if (sample_valid(cic->seek_samples) && cic->seek_mean > 131072) sl = 2; mod_timer(&cfqd->idle_slice_timer, jiffies + sl); return 1; } static void cfq_dispatch_insert(request_queue_t *q, struct cfq_rq *crq) { struct cfq_data *cfqd = q->elevator->elevator_data; struct cfq_queue *cfqq = crq->cfq_queue; cfqq->next_crq = cfq_find_next_crq(cfqd, cfqq, crq); cfq_remove_request(crq->request); cfqq->on_dispatch[cfq_crq_is_sync(crq)]++; elv_dispatch_sort(q, crq->request); } /* * return expired entry, or NULL to just start from scratch in rbtree */ static inline struct cfq_rq *cfq_check_fifo(struct cfq_queue *cfqq) { struct cfq_data *cfqd = cfqq->cfqd; struct request *rq; struct cfq_rq *crq; if (cfq_cfqq_fifo_expire(cfqq)) return NULL; if (!list_empty(&cfqq->fifo)) { int fifo = cfq_cfqq_class_sync(cfqq); crq = RQ_DATA(list_entry_fifo(cfqq->fifo.next)); rq = crq->request; if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) { cfq_mark_cfqq_fifo_expire(cfqq); return crq; } } return NULL; } /* * Scale schedule slice based on io priority. Use the sync time slice only * if a queue is marked sync and has sync io queued. A sync queue with async * io only, should not get full sync slice length. */ static inline int cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) { const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)]; WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio)); } static inline void cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) { cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies; } static inline int cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) { const int base_rq = cfqd->cfq_slice_async_rq; WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio)); } /* * get next queue for service */ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) { unsigned long now = jiffies; struct cfq_queue *cfqq; cfqq = cfqd->active_queue; if (!cfqq) goto new_queue; /* * slice has expired */ if (!cfq_cfqq_must_dispatch(cfqq) && time_after(now, cfqq->slice_end)) goto expire; /* * if queue has requests, dispatch one. if not, check if * enough slice is left to wait for one */ if (!RB_EMPTY(&cfqq->sort_list)) goto keep_queue; else if (cfq_cfqq_class_sync(cfqq) && time_before(now, cfqq->slice_end)) { if (cfq_arm_slice_timer(cfqd, cfqq)) return NULL; } expire: cfq_slice_expired(cfqd, 0); new_queue: cfqq = cfq_set_active_queue(cfqd); keep_queue: return cfqq; } static int __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq, int max_dispatch) { int dispatched = 0; BUG_ON(RB_EMPTY(&cfqq->sort_list)); do { struct cfq_rq *crq; /* * follow expired path, else get first next available */ if ((crq = cfq_check_fifo(cfqq)) == NULL) crq = cfqq->next_crq; /* * finally, insert request into driver dispatch list */ cfq_dispatch_insert(cfqd->queue, crq); cfqd->dispatch_slice++; dispatched++; if (!cfqd->active_cic) { atomic_inc(&crq->io_context->ioc->refcount); cfqd->active_cic = crq->io_context; } if (RB_EMPTY(&cfqq->sort_list)) break; } while (dispatched < max_dispatch); /* * if slice end isn't set yet, set it. if at least one request was * sync, use the sync time slice value */ if (!cfqq->slice_end) cfq_set_prio_slice(cfqd, cfqq); /* * expire an async queue immediately if it has used up its slice. idle * queue always expire after 1 dispatch round. */ if ((!cfq_cfqq_sync(cfqq) && cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) || cfq_class_idle(cfqq)) cfq_slice_expired(cfqd, 0); return dispatched; } static int cfq_forced_dispatch_cfqqs(struct list_head *list) { int dispatched = 0; struct cfq_queue *cfqq, *next; struct cfq_rq *crq; list_for_each_entry_safe(cfqq, next, list, cfq_list) { while ((crq = cfqq->next_crq)) { cfq_dispatch_insert(cfqq->cfqd->queue, crq); dispatched++; } BUG_ON(!list_empty(&cfqq->fifo)); } return dispatched; } static int cfq_forced_dispatch(struct cfq_data *cfqd) { int i, dispatched = 0; for (i = 0; i < CFQ_PRIO_LISTS; i++) dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]); dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr); dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr); dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr); cfq_slice_expired(cfqd, 0); BUG_ON(cfqd->busy_queues); return dispatched; } static int cfq_dispatch_requests(request_queue_t *q, int force) { struct cfq_data *cfqd = q->elevator->elevator_data; struct cfq_queue *cfqq; if (!cfqd->busy_queues) return 0; if (unlikely(force)) return cfq_forced_dispatch(cfqd); cfqq = cfq_select_queue(cfqd); if (cfqq) { int max_dispatch; cfq_clear_cfqq_must_dispatch(cfqq); cfq_clear_cfqq_wait_request(cfqq); del_timer(&cfqd->idle_slice_timer); max_dispatch = cfqd->cfq_quantum; if (cfq_class_idle(cfqq)) max_dispatch = 1; return __cfq_dispatch_requests(cfqd, cfqq, max_dispatch); } return 0; } /* * task holds one reference to the queue, dropped when task exits. each crq * in-flight on this queue also holds a reference, dropped when crq is freed. * * queue lock must be held here. */ static void cfq_put_queue(struct cfq_queue *cfqq) { struct cfq_data *cfqd = cfqq->cfqd; BUG_ON(atomic_read(&cfqq->ref) <= 0); if (!atomic_dec_and_test(&cfqq->ref)) return; BUG_ON(rb_first(&cfqq->sort_list)); BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]); BUG_ON(cfq_cfqq_on_rr(cfqq)); if (unlikely(cfqd->active_queue == cfqq)) __cfq_slice_expired(cfqd, cfqq, 0); /* * it's on the empty list and still hashed */ list_del(&cfqq->cfq_list); hlist_del(&cfqq->cfq_hash); kmem_cache_free(cfq_pool, cfqq); } static inline struct cfq_queue * __cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio, const int hashval) { struct hlist_head *hash_list = &cfqd->cfq_hash[hashval]; struct hlist_node *entry; struct cfq_queue *__cfqq; hlist_for_each_entry(__cfqq, entry, hash_list, cfq_hash) { const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio); if (__cfqq->key == key && (__p == prio || !prio)) return __cfqq; } return NULL; } static struct cfq_queue * cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio) { return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT)); } static void cfq_free_io_context(struct io_context *ioc) { struct cfq_io_context *__cic; struct rb_node *n; int freed = 0; while ((n = rb_first(&ioc->cic_root)) != NULL) { __cic = rb_entry(n, struct cfq_io_context, rb_node); rb_erase(&__cic->rb_node, &ioc->cic_root); kmem_cache_free(cfq_ioc_pool, __cic); freed++; } if (atomic_sub_and_test(freed, &ioc_count) && ioc_gone) complete(ioc_gone); } static void cfq_trim(struct io_context *ioc) { ioc->set_ioprio = NULL; cfq_free_io_context(ioc); } /* * Called with interrupts disabled */ static void cfq_exit_single_io_context(struct cfq_io_context *cic) { struct cfq_data *cfqd = cic->key; request_queue_t *q; if (!cfqd) return; q = cfqd->queue; WARN_ON(!irqs_disabled()); spin_lock(q->queue_lock); if (cic->cfqq[ASYNC]) { if (unlikely(cic->cfqq[ASYNC] == cfqd->active_queue)) __cfq_slice_expired(cfqd, cic->cfqq[ASYNC], 0); cfq_put_queue(cic->cfqq[ASYNC]); cic->cfqq[ASYNC] = NULL; } if (cic->cfqq[SYNC]) { if (unlikely(cic->cfqq[SYNC] == cfqd->active_queue)) __cfq_slice_expired(cfqd, cic->cfqq[SYNC], 0); cfq_put_queue(cic->cfqq[SYNC]); cic->cfqq[SYNC] = NULL; } cic->key = NULL; list_del_init(&cic->queue_list); spin_unlock(q->queue_lock); } static void cfq_exit_io_context(struct io_context *ioc) { struct cfq_io_context *__cic; unsigned long flags; struct rb_node *n; /* * put the reference this task is holding to the various queues */ read_lock_irqsave(&cfq_exit_lock, flags); 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); } read_unlock_irqrestore(&cfq_exit_lock, flags); } static struct cfq_io_context * cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) { struct cfq_io_context *cic = kmem_cache_alloc(cfq_ioc_pool, gfp_mask); if (cic) { RB_CLEAR(&cic->rb_node); cic->key = NULL; cic->cfqq[ASYNC] = NULL; cic->cfqq[SYNC] = NULL; cic->last_end_request = jiffies; cic->ttime_total = 0; cic->ttime_samples = 0; cic->ttime_mean = 0; cic->dtor = cfq_free_io_context; cic->exit = cfq_exit_io_context; INIT_LIST_HEAD(&cic->queue_list); atomic_inc(&ioc_count); } return cic; } static void cfq_init_prio_data(struct cfq_queue *cfqq) { struct task_struct *tsk = current; int ioprio_class; if (!cfq_cfqq_prio_changed(cfqq)) return; ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio); switch (ioprio_class) { default: printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class); case IOPRIO_CLASS_NONE: /* * no prio set, place us in the middle of the BE classes */ cfqq->ioprio = task_nice_ioprio(tsk); cfqq->ioprio_class = IOPRIO_CLASS_BE; break; case IOPRIO_CLASS_RT: cfqq->ioprio = task_ioprio(tsk); cfqq->ioprio_class = IOPRIO_CLASS_RT; break; case IOPRIO_CLASS_BE: cfqq->ioprio = task_ioprio(tsk); cfqq->ioprio_class = IOPRIO_CLASS_BE; break; case IOPRIO_CLASS_IDLE: cfqq->ioprio_class = IOPRIO_CLASS_IDLE; cfqq->ioprio = 7; cfq_clear_cfqq_idle_window(cfqq); break; } /* * keep track of original prio settings in case we have to temporarily * elevate the priority of this queue */ cfqq->org_ioprio = cfqq->ioprio; cfqq->org_ioprio_class = cfqq->ioprio_class; if (cfq_cfqq_on_rr(cfqq)) cfq_resort_rr_list(cfqq, 0); cfq_clear_cfqq_prio_changed(cfqq); } static inline void changed_ioprio(struct cfq_io_context *cic) { struct cfq_data *cfqd = cic->key; struct cfq_queue *cfqq; if (cfqd) { spin_lock(cfqd->queue->queue_lock); cfqq = cic->cfqq[ASYNC]; if (cfqq) { struct cfq_queue *new_cfqq; new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC, cic->ioc->task, GFP_ATOMIC); if (new_cfqq) { cic->cfqq[ASYNC] = new_cfqq; cfq_put_queue(cfqq); } } cfqq = cic->cfqq[SYNC]; if (cfqq) { cfq_mark_cfqq_prio_changed(cfqq); cfq_init_prio_data(cfqq); } spin_unlock(cfqd->queue->queue_lock); } } /* * callback from sys_ioprio_set, irqs are disabled */ static int cfq_ioc_set_ioprio(struct io_context *ioc, unsigned int ioprio) { struct cfq_io_context *cic; struct rb_node *n; write_lock(&cfq_exit_lock); 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); } write_unlock(&cfq_exit_lock); return 0; } static struct cfq_queue * cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask) { const int hashval = hash_long(key, CFQ_QHASH_SHIFT); struct cfq_queue *cfqq, *new_cfqq = NULL; unsigned short ioprio; retry: ioprio = tsk->ioprio; cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval); if (!cfqq) { if (new_cfqq) { cfqq = new_cfqq; new_cfqq = NULL; } else if (gfp_mask & __GFP_WAIT) { spin_unlock_irq(cfqd->queue->queue_lock); new_cfqq = kmem_cache_alloc(cfq_pool, gfp_mask); spin_lock_irq(cfqd->queue->queue_lock); goto retry; } else { cfqq = kmem_cache_alloc(cfq_pool, gfp_mask); if (!cfqq) goto out; } memset(cfqq, 0, sizeof(*cfqq)); INIT_HLIST_NODE(&cfqq->cfq_hash); INIT_LIST_HEAD(&cfqq->cfq_list); RB_CLEAR_ROOT(&cfqq->sort_list); INIT_LIST_HEAD(&cfqq->fifo); cfqq->key = key; hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]); atomic_set(&cfqq->ref, 0); cfqq->cfqd = cfqd; cfqq->service_last = 0; /* * set ->slice_left to allow preemption for a new process */ cfqq->slice_left = 2 * cfqd->cfq_slice_idle; cfq_mark_cfqq_idle_window(cfqq); cfq_mark_cfqq_prio_changed(cfqq); cfq_init_prio_data(cfqq); } if (new_cfqq) kmem_cache_free(cfq_pool, new_cfqq); atomic_inc(&cfqq->ref); out: WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq); return cfqq; } static void cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic) { read_lock(&cfq_exit_lock); rb_erase(&cic->rb_node, &ioc->cic_root); read_unlock(&cfq_exit_lock); kmem_cache_free(cfq_ioc_pool, cic); atomic_dec(&ioc_count); } static struct cfq_io_context * cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc) { struct rb_node *n; struct cfq_io_context *cic; void *k, *key = cfqd; restart: n = ioc->cic_root.rb_node; while (n) { cic = rb_entry(n, struct cfq_io_context, rb_node); /* ->key must be copied to avoid race with cfq_exit_queue() */ k = cic->key; if (unlikely(!k)) { cfq_drop_dead_cic(ioc, cic); goto restart; } if (key < k) n = n->rb_left; else if (key > k) n = n->rb_right; else return cic; } return NULL; } static inline void cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, struct cfq_io_context *cic) { struct rb_node **p; struct rb_node *parent; struct cfq_io_context *__cic; void *k; cic->ioc = ioc; cic->key = cfqd; ioc->set_ioprio = cfq_ioc_set_ioprio; 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(); } read_lock(&cfq_exit_lock); rb_link_node(&cic->rb_node, parent, p); rb_insert_color(&cic->rb_node, &ioc->cic_root); list_add(&cic->queue_list, &cfqd->cic_list); read_unlock(&cfq_exit_lock); } /* * 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); 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: return cic; err: put_io_context(ioc); return NULL; } static void cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic) { unsigned long elapsed, ttime; /* * if this context already has stuff queued, thinktime is from * last queue not last end */ #if 0 if (time_after(cic->last_end_request, cic->last_queue)) elapsed = jiffies - cic->last_end_request; else elapsed = jiffies - cic->last_queue; #else elapsed = jiffies - cic->last_end_request; #endif ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle); cic->ttime_samples = (7*cic->ttime_samples + 256) / 8; cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8; cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples; } static void cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic, struct cfq_rq *crq) { sector_t sdist; u64 total; if (cic->last_request_pos < crq->request->sector) sdist = crq->request->sector - cic->last_request_pos; else sdist = cic->last_request_pos - crq->request->sector; /* * Don't allow the seek distance to get too large from the * odd fragment, pagein, etc */ if (cic->seek_samples <= 60) /* second&third seek */ sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024); else sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64); cic->seek_samples = (7*cic->seek_samples + 256) / 8; cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8; total = cic->seek_total + (cic->seek_samples/2); do_div(total, cic->seek_samples); cic->seek_mean = (sector_t)total; } /* * Disable idle window if the process thinks too long or seeks so much that * it doesn't matter */ static void cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, struct cfq_io_context *cic) { int enable_idle = cfq_cfqq_idle_window(cfqq); if (!cic->ioc->task || !cfqd->cfq_slice_idle) 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 cfq_rq *crq) { struct cfq_queue *cfqq = cfqd->active_queue; if (cfq_class_idle(new_cfqq)) return 0; if (!cfqq) return 1; if (cfq_class_idle(cfqq)) return 1; if (!cfq_cfqq_wait_request(new_cfqq)) return 0; /* * if it doesn't have slice left, forget it */ if (new_cfqq->slice_left < cfqd->cfq_slice_idle) return 0; if (cfq_crq_is_sync(crq) && !cfq_cfqq_sync(cfqq)) 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) { struct cfq_queue *__cfqq, *next; list_for_each_entry_safe(__cfqq, next, &cfqd->cur_rr, cfq_list) cfq_resort_rr_list(__cfqq, 1); if (!cfqq->slice_left) cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2; cfqq->slice_end = cfqq->slice_left + jiffies; __cfq_slice_expired(cfqd, cfqq, 1); __cfq_set_active_queue(cfqd, cfqq); } /* * should really be a ll_rw_blk.c helper */ static void cfq_start_queueing(struct cfq_data *cfqd, struct cfq_queue *cfqq) { request_queue_t *q = cfqd->queue; if (!blk_queue_plugged(q)) q->request_fn(q); else __generic_unplug_device(q); } /* * Called when a new fs request (crq) is added (to cfqq). Check if there's * something we should do about it */ static void cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, struct cfq_rq *crq) { struct cfq_io_context *cic; cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq); /* * we never wait for an async request and we don't allow preemption * of an async request. so just return early */ if (!cfq_crq_is_sync(crq)) return; cic = crq->io_context; cfq_update_io_thinktime(cfqd, cic); cfq_update_io_seektime(cfqd, cic, crq); cfq_update_idle_window(cfqd, cfqq, cic); cic->last_queue = jiffies; cic->last_request_pos = crq->request->sector + crq->request->nr_sectors; if (cfqq == cfqd->active_queue) { /* * if we are waiting for a request for this queue, let it rip * immediately and flag that we must not expire this queue * just now */ if (cfq_cfqq_wait_request(cfqq)) { cfq_mark_cfqq_must_dispatch(cfqq); del_timer(&cfqd->idle_slice_timer); cfq_start_queueing(cfqd, cfqq); } } else if (cfq_should_preempt(cfqd, cfqq, crq)) { /* * 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); cfq_start_queueing(cfqd, cfqq); } } static void cfq_insert_request(request_queue_t *q, struct request *rq) { struct cfq_data *cfqd = q->elevator->elevator_data; struct cfq_rq *crq = RQ_DATA(rq); struct cfq_queue *cfqq = crq->cfq_queue; cfq_init_prio_data(cfqq); cfq_add_crq_rb(crq); list_add_tail(&rq->queuelist, &cfqq->fifo); if (rq_mergeable(rq)) cfq_add_crq_hash(cfqd, crq); cfq_crq_enqueued(cfqd, cfqq, crq); } static void cfq_completed_request(request_queue_t *q, struct request *rq) { struct cfq_rq *crq = RQ_DATA(rq); struct cfq_queue *cfqq = crq->cfq_queue; struct cfq_data *cfqd = cfqq->cfqd; const int sync = cfq_crq_is_sync(crq); unsigned long now; now = jiffies; WARN_ON(!cfqd->rq_in_driver); WARN_ON(!cfqq->on_dispatch[sync]); cfqd->rq_in_driver--; cfqq->on_dispatch[sync]--; if (!cfq_class_idle(cfqq)) cfqd->last_end_request = now; if (!cfq_cfqq_dispatched(cfqq)) { if (cfq_cfqq_on_rr(cfqq)) { cfqq->service_last = now; cfq_resort_rr_list(cfqq, 0); } cfq_schedule_dispatch(cfqd); } if (cfq_crq_is_sync(crq)) crq->io_context->last_end_request = now; } static struct request * cfq_former_request(request_queue_t *q, struct request *rq) { struct cfq_rq *crq = RQ_DATA(rq); struct rb_node *rbprev = rb_prev(&crq->rb_node); if (rbprev) return rb_entry_crq(rbprev)->request; return NULL; } static struct request * cfq_latter_request(request_queue_t *q, struct request *rq) { struct cfq_rq *crq = RQ_DATA(rq); struct rb_node *rbnext = rb_next(&crq->rb_node); if (rbnext) return rb_entry_crq(rbnext)->request; return NULL; } /* * we temporarily boost lower priority queues if they are holding fs exclusive * resources. they are boosted to normal prio (CLASS_BE/4) */ static void cfq_prio_boost(struct cfq_queue *cfqq) { const int ioprio_class = cfqq->ioprio_class; const int ioprio = cfqq->ioprio; if (has_fs_excl()) { /* * boost idle prio on transactions that would lock out other * users of the filesystem */ if (cfq_class_idle(cfqq)) cfqq->ioprio_class = IOPRIO_CLASS_BE; if (cfqq->ioprio > IOPRIO_NORM) cfqq->ioprio = IOPRIO_NORM; } else { /* * check if we need to unboost the queue */ if (cfqq->ioprio_class != cfqq->org_ioprio_class) cfqq->ioprio_class = cfqq->org_ioprio_class; if (cfqq->ioprio != cfqq->org_ioprio) cfqq->ioprio = cfqq->org_ioprio; } /* * refile between round-robin lists if we moved the priority class */ if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio) && cfq_cfqq_on_rr(cfqq)) cfq_resort_rr_list(cfqq, 0); } static inline int __cfq_may_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq, struct task_struct *task, int rw) { #if 1 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; #else if (!cfqq || task->flags & PF_MEMALLOC) return ELV_MQUEUE_MAY; if (!cfqq->allocated[rw] || cfq_cfqq_must_alloc(cfqq)) { if (cfq_cfqq_wait_request(cfqq)) return ELV_MQUEUE_MUST; /* * only allow 1 ELV_MQUEUE_MUST per slice, otherwise we * can quickly flood the queue with writes from a single task */ if (rw == READ || !cfq_cfqq_must_alloc_slice(cfqq)) { cfq_mark_cfqq_must_alloc_slice(cfqq); return ELV_MQUEUE_MUST; } return ELV_MQUEUE_MAY; } if (cfq_class_idle(cfqq)) return ELV_MQUEUE_NO; if (cfqq->allocated[rw] >= cfqd->max_queued) { struct io_context *ioc = get_io_context(GFP_ATOMIC); int ret = ELV_MQUEUE_NO; if (ioc && ioc->nr_batch_requests) ret = ELV_MQUEUE_MAY; put_io_context(ioc); return ret; } return ELV_MQUEUE_MAY; #endif } static int cfq_may_queue(request_queue_t *q, int rw, struct bio *bio) { struct cfq_data *cfqd = q->elevator->elevator_data; struct task_struct *tsk = current; struct cfq_queue *cfqq; /* * don't force setup of a queue from here, as a call to may_queue * does not necessarily imply that a request actually will be queued. * so just lookup a possibly existing queue, or return 'may queue' * if that fails */ cfqq = cfq_find_cfq_hash(cfqd, cfq_queue_pid(tsk, rw), tsk->ioprio); if (cfqq) { cfq_init_prio_data(cfqq); cfq_prio_boost(cfqq); return __cfq_may_queue(cfqd, cfqq, tsk, rw); } return ELV_MQUEUE_MAY; } static void cfq_check_waiters(request_queue_t *q, struct cfq_queue *cfqq) { struct cfq_data *cfqd = q->elevator->elevator_data; struct request_list *rl = &q->rq; if (cfqq->allocated[READ] <= cfqd->max_queued || cfqd->rq_starved) { smp_mb(); if (waitqueue_active(&rl->wait[READ])) wake_up(&rl->wait[READ]); } if (cfqq->allocated[WRITE] <= cfqd->max_queued || cfqd->rq_starved) { smp_mb(); if (waitqueue_active(&rl->wait[WRITE])) wake_up(&rl->wait[WRITE]); } } /* * queue lock held here */ static void cfq_put_request(request_queue_t *q, struct request *rq) { struct cfq_data *cfqd = q->elevator->elevator_data; struct cfq_rq *crq = RQ_DATA(rq); if (crq) { struct cfq_queue *cfqq = crq->cfq_queue; const int rw = rq_data_dir(rq); BUG_ON(!cfqq->allocated[rw]); cfqq->allocated[rw]--; put_io_context(crq->io_context->ioc); mempool_free(crq, cfqd->crq_pool); rq->elevator_private = NULL; cfq_check_waiters(q, cfqq); cfq_put_queue(cfqq); } } /* * Allocate cfq data structures associated with this request. */ static int cfq_set_request(request_queue_t *q, struct request *rq, struct bio *bio, gfp_t gfp_mask) { struct cfq_data *cfqd = q->elevator->elevator_data; struct task_struct *tsk = current; struct cfq_io_context *cic; const int rw = rq_data_dir(rq); pid_t key = cfq_queue_pid(tsk, rw); struct cfq_queue *cfqq; struct cfq_rq *crq; unsigned long flags; int is_sync = key != CFQ_KEY_ASYNC; might_sleep_if(gfp_mask & __GFP_WAIT); cic = cfq_get_io_context(cfqd, gfp_mask); spin_lock_irqsave(q->queue_lock, flags); if (!cic) goto queue_fail; if (!cic->cfqq[is_sync]) { cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask); if (!cfqq) goto queue_fail; cic->cfqq[is_sync] = cfqq; } else cfqq = cic->cfqq[is_sync]; cfqq->allocated[rw]++; cfq_clear_cfqq_must_alloc(cfqq); cfqd->rq_starved = 0; atomic_inc(&cfqq->ref); spin_unlock_irqrestore(q->queue_lock, flags); crq = mempool_alloc(cfqd->crq_pool, gfp_mask); if (crq) { RB_CLEAR(&crq->rb_node); crq->rb_key = 0; crq->request = rq; INIT_HLIST_NODE(&crq->hash); crq->cfq_queue = cfqq; crq->io_context = cic; if (is_sync) cfq_mark_crq_is_sync(crq); else cfq_clear_crq_is_sync(crq); rq->elevator_private = crq; return 0; } spin_lock_irqsave(q->queue_lock, flags); cfqq->allocated[rw]--; if (!(cfqq->allocated[0] + cfqq->allocated[1])) cfq_mark_cfqq_must_alloc(cfqq); cfq_put_queue(cfqq); queue_fail: if (cic) put_io_context(cic->ioc); /* * mark us rq allocation starved. we need to kickstart the process * ourselves if there are no pending requests that can do it for us. * that would be an extremely rare OOM situation */ cfqd->rq_starved = 1; cfq_schedule_dispatch(cfqd); spin_unlock_irqrestore(q->queue_lock, flags); return 1; } static void cfq_kick_queue(void *data) { request_queue_t *q = data; struct cfq_data *cfqd = q->elevator->elevator_data; unsigned long flags; spin_lock_irqsave(q->queue_lock, flags); if (cfqd->rq_starved) { struct request_list *rl = &q->rq; /* * we aren't guaranteed to get a request after this, but we * have to be opportunistic */ smp_mb(); if (waitqueue_active(&rl->wait[READ])) wake_up(&rl->wait[READ]); if (waitqueue_active(&rl->wait[WRITE])) wake_up(&rl->wait[WRITE]); } blk_remove_plug(q); q->request_fn(q); spin_unlock_irqrestore(q->queue_lock, flags); } /* * Timer running if the active_queue is currently idling inside its time slice */ static void cfq_idle_slice_timer(unsigned long data) { struct cfq_data *cfqd = (struct cfq_data *) data; struct cfq_queue *cfqq; unsigned long flags; spin_lock_irqsave(cfqd->queue->queue_lock, flags); if ((cfqq = cfqd->active_queue) != NULL) { unsigned long now = jiffies; /* * expired */ if (time_after(now, cfqq->slice_end)) goto expire; /* * only expire and reinvoke request handler, if there are * other queues with pending requests */ if (!cfqd->busy_queues) { cfqd->idle_slice_timer.expires = min(now + cfqd->cfq_slice_idle, cfqq->slice_end); add_timer(&cfqd->idle_slice_timer); goto out_cont; } /* * not expired and it has a request pending, let it dispatch */ if (!RB_EMPTY(&cfqq->sort_list)) { cfq_mark_cfqq_must_dispatch(cfqq); goto out_kick; } } expire: cfq_slice_expired(cfqd, 0); out_kick: cfq_schedule_dispatch(cfqd); out_cont: spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); } /* * Timer running if an idle class queue is waiting for service */ static void cfq_idle_class_timer(unsigned long data) { struct cfq_data *cfqd = (struct cfq_data *) data; unsigned long flags, end; spin_lock_irqsave(cfqd->queue->queue_lock, flags); /* * race with a non-idle queue, reset timer */ end = cfqd->last_end_request + CFQ_IDLE_GRACE; if (!time_after_eq(jiffies, end)) { cfqd->idle_class_timer.expires = end; add_timer(&cfqd->idle_class_timer); } else cfq_schedule_dispatch(cfqd); spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); } static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) { del_timer_sync(&cfqd->idle_slice_timer); del_timer_sync(&cfqd->idle_class_timer); blk_sync_queue(cfqd->queue); } static void cfq_exit_queue(elevator_t *e) { struct cfq_data *cfqd = e->elevator_data; request_queue_t *q = cfqd->queue; cfq_shutdown_timer_wq(cfqd); write_lock(&cfq_exit_lock); 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); if (cic->cfqq[ASYNC]) { cfq_put_queue(cic->cfqq[ASYNC]); cic->cfqq[ASYNC] = NULL; } if (cic->cfqq[SYNC]) { cfq_put_queue(cic->cfqq[SYNC]); cic->cfqq[SYNC] = NULL; } cic->key = NULL; list_del_init(&cic->queue_list); } spin_unlock_irq(q->queue_lock); write_unlock(&cfq_exit_lock); cfq_shutdown_timer_wq(cfqd); mempool_destroy(cfqd->crq_pool); kfree(cfqd->crq_hash); kfree(cfqd->cfq_hash); kfree(cfqd); } static int cfq_init_queue(request_queue_t *q, elevator_t *e) { struct cfq_data *cfqd; int i; cfqd = kmalloc(sizeof(*cfqd), GFP_KERNEL); if (!cfqd) return -ENOMEM; memset(cfqd, 0, sizeof(*cfqd)); for (i = 0; i < CFQ_PRIO_LISTS; i++) INIT_LIST_HEAD(&cfqd->rr_list[i]); INIT_LIST_HEAD(&cfqd->busy_rr); INIT_LIST_HEAD(&cfqd->cur_rr); INIT_LIST_HEAD(&cfqd->idle_rr); INIT_LIST_HEAD(&cfqd->empty_list); INIT_LIST_HEAD(&cfqd->cic_list); cfqd->crq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_MHASH_ENTRIES, GFP_KERNEL); if (!cfqd->crq_hash) goto out_crqhash; cfqd->cfq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL); if (!cfqd->cfq_hash) goto out_cfqhash; cfqd->crq_pool = mempool_create_slab_pool(BLKDEV_MIN_RQ, crq_pool); if (!cfqd->crq_pool) goto out_crqpool; for (i = 0; i < CFQ_MHASH_ENTRIES; i++) INIT_HLIST_HEAD(&cfqd->crq_hash[i]); for (i = 0; i < CFQ_QHASH_ENTRIES; i++) INIT_HLIST_HEAD(&cfqd->cfq_hash[i]); e->elevator_data = cfqd; cfqd->queue = q; cfqd->max_queued = q->nr_requests / 4; q->nr_batching = cfq_queued; init_timer(&cfqd->idle_slice_timer); cfqd->idle_slice_timer.function = cfq_idle_slice_timer; cfqd->idle_slice_timer.data = (unsigned long) cfqd; init_timer(&cfqd->idle_class_timer); cfqd->idle_class_timer.function = cfq_idle_class_timer; cfqd->idle_class_timer.data = (unsigned long) cfqd; INIT_WORK(&cfqd->unplug_work, cfq_kick_queue, q); cfqd->cfq_queued = cfq_queued; 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 0; out_crqpool: kfree(cfqd->cfq_hash); out_cfqhash: kfree(cfqd->crq_hash); out_crqhash: kfree(cfqd); return -ENOMEM; } static void cfq_slab_kill(void) { if (crq_pool) kmem_cache_destroy(crq_pool); 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) { crq_pool = kmem_cache_create("crq_pool", sizeof(struct cfq_rq), 0, 0, NULL, NULL); if (!crq_pool) goto fail; cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0, NULL, NULL); if (!cfq_pool) goto fail; cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool", sizeof(struct cfq_io_context), 0, 0, NULL, NULL); if (!cfq_ioc_pool) goto fail; return 0; fail: cfq_slab_kill(); return -ENOMEM; } /* * sysfs parts below --> */ static ssize_t cfq_var_show(unsigned int var, char *page) { return sprintf(page, "%d\n", var); } static ssize_t cfq_var_store(unsigned int *var, const char *page, size_t count) { char *p = (char *) page; *var = simple_strtoul(p, &p, 10); return count; } #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ static ssize_t __FUNC(elevator_t *e, char *page) \ { \ struct cfq_data *cfqd = e->elevator_data; \ unsigned int __data = __VAR; \ if (__CONV) \ __data = jiffies_to_msecs(__data); \ return cfq_var_show(__data, (page)); \ } SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0); SHOW_FUNCTION(cfq_queued_show, cfqd->cfq_queued, 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_queued_store, &cfqd->cfq_queued, 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(queued), CFQ_ATTR(fifo_expire_sync), CFQ_ATTR(fifo_expire_async), CFQ_ATTR(back_seek_max), CFQ_ATTR(back_seek_penalty), CFQ_ATTR(slice_sync), CFQ_ATTR(slice_async), CFQ_ATTR(slice_async_rq), CFQ_ATTR(slice_idle), __ATTR_NULL }; static struct elevator_type iosched_cfq = { .ops = { .elevator_merge_fn = cfq_merge, .elevator_merged_fn = cfq_merged_request, .elevator_merge_req_fn = cfq_merged_requests, .elevator_dispatch_fn = cfq_dispatch_requests, .elevator_add_req_fn = cfq_insert_request, .elevator_activate_req_fn = cfq_activate_request, .elevator_deactivate_req_fn = cfq_deactivate_request, .elevator_queue_empty_fn = cfq_queue_empty, .elevator_completed_req_fn = cfq_completed_request, .elevator_former_req_fn = cfq_former_request, .elevator_latter_req_fn = cfq_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_trim, }, .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(all_gone); elv_unregister(&iosched_cfq); 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(); 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");