/* * 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 /* * tunables */ static const int cfq_quantum = 4; /* max queue in one round of service */ static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 }; static const int cfq_back_max = 16 * 1024; /* maximum backwards seek, in KiB */ static const int cfq_back_penalty = 2; /* penalty of a backwards seek */ static const int cfq_slice_sync = HZ / 10; static int cfq_slice_async = HZ / 25; static const int cfq_slice_async_rq = 2; static int cfq_slice_idle = HZ / 125; /* * grace period before allowing idle class to get disk access */ #define CFQ_IDLE_GRACE (HZ / 10) /* * below this threshold, we consider thinktime immediate */ #define CFQ_MIN_TT (2) #define CFQ_SLICE_SCALE (5) #define RQ_CIC(rq) ((struct cfq_io_context*)(rq)->elevator_private) #define RQ_CFQQ(rq) ((rq)->elevator_private2) static struct kmem_cache *cfq_pool; static struct kmem_cache *cfq_ioc_pool; static DEFINE_PER_CPU(unsigned long, ioc_count); static struct completion *ioc_gone; #define CFQ_PRIO_LISTS IOPRIO_BE_NR #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE) #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT) #define ASYNC (0) #define SYNC (1) #define sample_valid(samples) ((samples) > 80) /* * Most of our rbtree usage is for sorting with min extraction, so * if we cache the leftmost node we don't have to walk down the tree * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should * move this into the elevator for the rq sorting as well. */ struct cfq_rb_root { struct rb_root rb; struct rb_node *left; }; #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, } /* * Per block device queue structure */ struct cfq_data { struct request_queue *queue; /* * rr list of queues with requests and the count of them */ struct cfq_rb_root service_tree; unsigned int busy_queues; int rq_in_driver; int sync_flight; int hw_tag; /* * idle window management */ struct timer_list idle_slice_timer; struct work_struct unplug_work; struct cfq_queue *active_queue; struct cfq_io_context *active_cic; /* * async queue for each priority case */ struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR]; struct cfq_queue *async_idle_cfqq; struct timer_list idle_class_timer; sector_t last_position; unsigned long last_end_request; /* * tunables, see top of file */ unsigned int cfq_quantum; unsigned int cfq_fifo_expire[2]; unsigned int cfq_back_penalty; unsigned int cfq_back_max; unsigned int cfq_slice[2]; unsigned int cfq_slice_async_rq; unsigned int cfq_slice_idle; struct list_head cic_list; }; /* * Per process-grouping structure */ struct cfq_queue { /* reference count */ atomic_t ref; /* parent cfq_data */ struct cfq_data *cfqd; /* service_tree member */ struct rb_node rb_node; /* service_tree key */ unsigned long rb_key; /* sorted list of pending requests */ struct rb_root sort_list; /* if fifo isn't expired, next request to serve */ struct request *next_rq; /* requests queued in sort_list */ int queued[2]; /* currently allocated requests */ int allocated[2]; /* pending metadata requests */ int meta_pending; /* fifo list of requests in sort_list */ struct list_head fifo; unsigned long slice_end; long slice_resid; /* number of requests that are on the dispatch list or inside driver */ int dispatched; /* io prio of this group */ unsigned short ioprio, org_ioprio; unsigned short ioprio_class, org_ioprio_class; /* various state flags, see below */ unsigned int flags; }; enum cfqq_state_flags { CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */ CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */ CFQ_CFQQ_FLAG_must_alloc, /* must be allowed rq alloc */ CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */ CFQ_CFQQ_FLAG_must_dispatch, /* must dispatch, even if expired */ CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */ CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */ CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */ CFQ_CFQQ_FLAG_queue_new, /* queue never been serviced */ CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */ CFQ_CFQQ_FLAG_sync, /* synchronous queue */ }; #define CFQ_CFQQ_FNS(name) \ static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \ { \ cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \ } \ static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \ { \ cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \ } \ static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \ { \ return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \ } CFQ_CFQQ_FNS(on_rr); CFQ_CFQQ_FNS(wait_request); CFQ_CFQQ_FNS(must_alloc); CFQ_CFQQ_FNS(must_alloc_slice); CFQ_CFQQ_FNS(must_dispatch); CFQ_CFQQ_FNS(fifo_expire); CFQ_CFQQ_FNS(idle_window); CFQ_CFQQ_FNS(prio_changed); CFQ_CFQQ_FNS(queue_new); CFQ_CFQQ_FNS(slice_new); CFQ_CFQQ_FNS(sync); #undef CFQ_CFQQ_FNS static void cfq_dispatch_insert(struct request_queue *, struct request *); static struct cfq_queue *cfq_get_queue(struct cfq_data *, int, struct task_struct *, gfp_t); static struct cfq_io_context *cfq_cic_rb_lookup(struct cfq_data *, struct io_context *); static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic, int is_sync) { return cic->cfqq[!!is_sync]; } static inline void cic_set_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq, int is_sync) { cic->cfqq[!!is_sync] = cfqq; } /* * We regard a request as SYNC, if it's either a read or has the SYNC bit * set (in which case it could also be direct WRITE). */ static inline int cfq_bio_sync(struct bio *bio) { if (bio_data_dir(bio) == READ || bio_sync(bio)) return 1; return 0; } /* * scheduler run of queue, if there are requests pending and no one in the * driver that will restart queueing */ static inline void cfq_schedule_dispatch(struct cfq_data *cfqd) { if (cfqd->busy_queues) kblockd_schedule_work(&cfqd->unplug_work); } static int cfq_queue_empty(struct request_queue *q) { struct cfq_data *cfqd = q->elevator->elevator_data; return !cfqd->busy_queues; } /* * Scale schedule slice based on io priority. Use the sync time slice only * if a queue is marked sync and has sync io queued. A sync queue with async * io only, should not get full sync slice length. */ static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync, unsigned short prio) { const int base_slice = cfqd->cfq_slice[sync]; WARN_ON(prio >= IOPRIO_BE_NR); return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio)); } static inline int cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) { return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio); } static inline void cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) { cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies; } /* * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end * isn't valid until the first request from the dispatch is activated * and the slice time set. */ static inline int cfq_slice_used(struct cfq_queue *cfqq) { if (cfq_cfqq_slice_new(cfqq)) return 0; if (time_before(jiffies, cfqq->slice_end)) return 0; return 1; } /* * Lifted from AS - choose which of rq1 and rq2 that is best served now. * We choose the request that is closest to the head right now. Distance * behind the head is penalized and only allowed to a certain extent. */ static struct request * cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2) { sector_t last, s1, s2, d1 = 0, d2 = 0; unsigned long back_max; #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */ #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */ unsigned wrap = 0; /* bit mask: requests behind the disk head? */ if (rq1 == NULL || rq1 == rq2) return rq2; if (rq2 == NULL) return rq1; if (rq_is_sync(rq1) && !rq_is_sync(rq2)) return rq1; else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) return rq2; if (rq_is_meta(rq1) && !rq_is_meta(rq2)) return rq1; else if (rq_is_meta(rq2) && !rq_is_meta(rq1)) return rq2; s1 = rq1->sector; s2 = rq2->sector; last = cfqd->last_position; /* * by definition, 1KiB is 2 sectors */ back_max = cfqd->cfq_back_max * 2; /* * Strict one way elevator _except_ in the case where we allow * short backward seeks which are biased as twice the cost of a * similar forward seek. */ if (s1 >= last) d1 = s1 - last; else if (s1 + back_max >= last) d1 = (last - s1) * cfqd->cfq_back_penalty; else wrap |= CFQ_RQ1_WRAP; if (s2 >= last) d2 = s2 - last; else if (s2 + back_max >= last) d2 = (last - s2) * cfqd->cfq_back_penalty; else wrap |= CFQ_RQ2_WRAP; /* Found required data */ /* * By doing switch() on the bit mask "wrap" we avoid having to * check two variables for all permutations: --> faster! */ switch (wrap) { case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ if (d1 < d2) return rq1; else if (d2 < d1) return rq2; else { if (s1 >= s2) return rq1; else return rq2; } case CFQ_RQ2_WRAP: return rq1; case CFQ_RQ1_WRAP: return rq2; case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */ default: /* * Since both rqs are wrapped, * start with the one that's further behind head * (--> only *one* back seek required), * since back seek takes more time than forward. */ if (s1 <= s2) return rq1; else return rq2; } } /* * The below is leftmost cache rbtree addon */ static struct rb_node *cfq_rb_first(struct cfq_rb_root *root) { if (!root->left) root->left = rb_first(&root->rb); return root->left; } static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root) { if (root->left == n) root->left = NULL; rb_erase(n, &root->rb); RB_CLEAR_NODE(n); } /* * would be nice to take fifo expire time into account as well */ static struct request * cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq, struct request *last) { struct rb_node *rbnext = rb_next(&last->rb_node); struct rb_node *rbprev = rb_prev(&last->rb_node); struct request *next = NULL, *prev = NULL; BUG_ON(RB_EMPTY_NODE(&last->rb_node)); if (rbprev) prev = rb_entry_rq(rbprev); if (rbnext) next = rb_entry_rq(rbnext); else { rbnext = rb_first(&cfqq->sort_list); if (rbnext && rbnext != &last->rb_node) next = rb_entry_rq(rbnext); } return cfq_choose_req(cfqd, next, prev); } static unsigned long cfq_slice_offset(struct cfq_data *cfqd, struct cfq_queue *cfqq) { /* * just an approximation, should be ok. */ return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) - cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio)); } /* * The cfqd->service_tree holds all pending cfq_queue's that have * requests waiting to be processed. It is sorted in the order that * we will service the queues. */ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, int add_front) { struct rb_node **p = &cfqd->service_tree.rb.rb_node; struct rb_node *parent = NULL; unsigned long rb_key; int left; if (!add_front) { rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; rb_key += cfqq->slice_resid; cfqq->slice_resid = 0; } else rb_key = 0; if (!RB_EMPTY_NODE(&cfqq->rb_node)) { /* * same position, nothing more to do */ if (rb_key == cfqq->rb_key) return; cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); } left = 1; while (*p) { struct cfq_queue *__cfqq; struct rb_node **n; parent = *p; __cfqq = rb_entry(parent, struct cfq_queue, rb_node); /* * sort RT queues first, we always want to give * preference to them. IDLE queues goes to the back. * after that, sort on the next service time. */ if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq)) n = &(*p)->rb_left; else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq)) n = &(*p)->rb_right; else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq)) n = &(*p)->rb_left; else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq)) n = &(*p)->rb_right; else if (rb_key < __cfqq->rb_key) n = &(*p)->rb_left; else n = &(*p)->rb_right; if (n == &(*p)->rb_right) left = 0; p = n; } if (left) cfqd->service_tree.left = &cfqq->rb_node; cfqq->rb_key = rb_key; rb_link_node(&cfqq->rb_node, parent, p); rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb); } /* * Update cfqq's position in the service tree. */ static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq) { /* * Resorting requires the cfqq to be on the RR list already. */ if (cfq_cfqq_on_rr(cfqq)) cfq_service_tree_add(cfqd, cfqq, 0); } /* * add to busy list of queues for service, trying to be fair in ordering * the pending list according to last request service */ static inline void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) { BUG_ON(cfq_cfqq_on_rr(cfqq)); cfq_mark_cfqq_on_rr(cfqq); cfqd->busy_queues++; cfq_resort_rr_list(cfqd, cfqq); } /* * Called when the cfqq no longer has requests pending, remove it from * the service tree. */ static inline void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) { BUG_ON(!cfq_cfqq_on_rr(cfqq)); cfq_clear_cfqq_on_rr(cfqq); if (!RB_EMPTY_NODE(&cfqq->rb_node)) cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); BUG_ON(!cfqd->busy_queues); cfqd->busy_queues--; } /* * rb tree support functions */ static inline void cfq_del_rq_rb(struct request *rq) { struct cfq_queue *cfqq = RQ_CFQQ(rq); struct cfq_data *cfqd = cfqq->cfqd; const int sync = rq_is_sync(rq); BUG_ON(!cfqq->queued[sync]); cfqq->queued[sync]--; elv_rb_del(&cfqq->sort_list, rq); if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) cfq_del_cfqq_rr(cfqd, cfqq); } static void cfq_add_rq_rb(struct request *rq) { struct cfq_queue *cfqq = RQ_CFQQ(rq); struct cfq_data *cfqd = cfqq->cfqd; struct request *__alias; cfqq->queued[rq_is_sync(rq)]++; /* * looks a little odd, but the first insert might return an alias. * if that happens, put the alias on the dispatch list */ while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL) cfq_dispatch_insert(cfqd->queue, __alias); if (!cfq_cfqq_on_rr(cfqq)) cfq_add_cfqq_rr(cfqd, cfqq); /* * check if this request is a better next-serve candidate */ cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq); BUG_ON(!cfqq->next_rq); } static inline void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq) { elv_rb_del(&cfqq->sort_list, rq); cfqq->queued[rq_is_sync(rq)]--; cfq_add_rq_rb(rq); } static struct request * cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio) { struct task_struct *tsk = current; struct cfq_io_context *cic; struct cfq_queue *cfqq; cic = cfq_cic_rb_lookup(cfqd, tsk->io_context); if (!cic) return NULL; cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); if (cfqq) { sector_t sector = bio->bi_sector + bio_sectors(bio); return elv_rb_find(&cfqq->sort_list, sector); } return NULL; } static void cfq_activate_request(struct request_queue *q, struct request *rq) { struct cfq_data *cfqd = q->elevator->elevator_data; cfqd->rq_in_driver++; /* * If the depth is larger 1, it really could be queueing. But lets * make the mark a little higher - idling could still be good for * low queueing, and a low queueing number could also just indicate * a SCSI mid layer like behaviour where limit+1 is often seen. */ if (!cfqd->hw_tag && cfqd->rq_in_driver > 4) cfqd->hw_tag = 1; cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors; } static void cfq_deactivate_request(struct request_queue *q, struct request *rq) { struct cfq_data *cfqd = q->elevator->elevator_data; WARN_ON(!cfqd->rq_in_driver); cfqd->rq_in_driver--; } static void cfq_remove_request(struct request *rq) { struct cfq_queue *cfqq = RQ_CFQQ(rq); if (cfqq->next_rq == rq) cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq); list_del_init(&rq->queuelist); cfq_del_rq_rb(rq); if (rq_is_meta(rq)) { WARN_ON(!cfqq->meta_pending); cfqq->meta_pending--; } } static int cfq_merge(struct request_queue *q, struct request **req, struct bio *bio) { struct cfq_data *cfqd = q->elevator->elevator_data; struct request *__rq; __rq = cfq_find_rq_fmerge(cfqd, bio); if (__rq && elv_rq_merge_ok(__rq, bio)) { *req = __rq; return ELEVATOR_FRONT_MERGE; } return ELEVATOR_NO_MERGE; } static void cfq_merged_request(struct request_queue *q, struct request *req, int type) { if (type == ELEVATOR_FRONT_MERGE) { struct cfq_queue *cfqq = RQ_CFQQ(req); cfq_reposition_rq_rb(cfqq, req); } } static void cfq_merged_requests(struct request_queue *q, struct request *rq, struct request *next) { /* * reposition in fifo if next is older than rq */ if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && time_before(next->start_time, rq->start_time)) list_move(&rq->queuelist, &next->queuelist); cfq_remove_request(next); } static int cfq_allow_merge(struct request_queue *q, struct request *rq, struct bio *bio) { struct cfq_data *cfqd = q->elevator->elevator_data; struct cfq_io_context *cic; struct cfq_queue *cfqq; /* * Disallow merge of a sync bio into an async request. */ if (cfq_bio_sync(bio) && !rq_is_sync(rq)) return 0; /* * Lookup the cfqq that this bio will be queued with. Allow * merge only if rq is queued there. */ cic = cfq_cic_rb_lookup(cfqd, current->io_context); if (!cic) return 0; cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); if (cfqq == RQ_CFQQ(rq)) return 1; return 0; } static inline void __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) { if (cfqq) { /* * stop potential idle class queues waiting service */ del_timer(&cfqd->idle_class_timer); cfqq->slice_end = 0; cfq_clear_cfqq_must_alloc_slice(cfqq); cfq_clear_cfqq_fifo_expire(cfqq); cfq_mark_cfqq_slice_new(cfqq); cfq_clear_cfqq_queue_new(cfqq); } cfqd->active_queue = cfqq; } /* * current cfqq expired its slice (or was too idle), select new one */ static void __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, int timed_out) { if (cfq_cfqq_wait_request(cfqq)) del_timer(&cfqd->idle_slice_timer); cfq_clear_cfqq_must_dispatch(cfqq); cfq_clear_cfqq_wait_request(cfqq); /* * store what was left of this slice, if the queue idled/timed out */ if (timed_out && !cfq_cfqq_slice_new(cfqq)) cfqq->slice_resid = cfqq->slice_end - jiffies; cfq_resort_rr_list(cfqd, cfqq); if (cfqq == cfqd->active_queue) cfqd->active_queue = NULL; if (cfqd->active_cic) { put_io_context(cfqd->active_cic->ioc); cfqd->active_cic = NULL; } } static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out) { struct cfq_queue *cfqq = cfqd->active_queue; if (cfqq) __cfq_slice_expired(cfqd, cfqq, timed_out); } /* * Get next queue for service. Unless we have a queue preemption, * we'll simply select the first cfqq in the service tree. */ static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) { struct cfq_queue *cfqq; struct rb_node *n; if (RB_EMPTY_ROOT(&cfqd->service_tree.rb)) return NULL; n = cfq_rb_first(&cfqd->service_tree); cfqq = rb_entry(n, struct cfq_queue, rb_node); if (cfq_class_idle(cfqq)) { unsigned long end; /* * if we have idle queues and no rt or be queues had * pending requests, either allow immediate service if * the grace period has passed or arm the idle grace * timer */ end = cfqd->last_end_request + CFQ_IDLE_GRACE; if (time_before(jiffies, end)) { mod_timer(&cfqd->idle_class_timer, end); cfqq = NULL; } } return cfqq; } /* * Get and set a new active queue for service. */ static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd) { struct cfq_queue *cfqq; cfqq = cfq_get_next_queue(cfqd); __cfq_set_active_queue(cfqd, cfqq); return cfqq; } static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd, struct request *rq) { if (rq->sector >= cfqd->last_position) return rq->sector - cfqd->last_position; else return cfqd->last_position - rq->sector; } static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq) { struct cfq_io_context *cic = cfqd->active_cic; if (!sample_valid(cic->seek_samples)) return 0; return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean; } static int cfq_close_cooperator(struct cfq_data *cfq_data, struct cfq_queue *cfqq) { /* * We should notice if some of the queues are cooperating, eg * working closely on the same area of the disk. In that case, * we can group them together and don't waste time idling. */ return 0; } #define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024)) static void cfq_arm_slice_timer(struct cfq_data *cfqd) { struct cfq_queue *cfqq = cfqd->active_queue; struct cfq_io_context *cic; unsigned long sl; WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list)); WARN_ON(cfq_cfqq_slice_new(cfqq)); /* * idle is disabled, either manually or by past process history */ if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq)) return; /* * task has exited, don't wait */ cic = cfqd->active_cic; if (!cic || !cic->ioc->task) return; /* * See if this prio level has a good candidate */ if (cfq_close_cooperator(cfqd, cfqq) && (sample_valid(cic->ttime_samples) && cic->ttime_mean > 2)) return; cfq_mark_cfqq_must_dispatch(cfqq); cfq_mark_cfqq_wait_request(cfqq); /* * we don't want to idle for seeks, but we do want to allow * fair distribution of slice time for a process doing back-to-back * seeks. so allow a little bit of time for him to submit a new rq */ sl = cfqd->cfq_slice_idle; if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic)) sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT)); mod_timer(&cfqd->idle_slice_timer, jiffies + sl); } /* * Move request from internal lists to the request queue dispatch list. */ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq) { struct cfq_data *cfqd = q->elevator->elevator_data; struct cfq_queue *cfqq = RQ_CFQQ(rq); cfq_remove_request(rq); cfqq->dispatched++; elv_dispatch_sort(q, rq); if (cfq_cfqq_sync(cfqq)) cfqd->sync_flight++; } /* * return expired entry, or NULL to just start from scratch in rbtree */ static inline struct request *cfq_check_fifo(struct cfq_queue *cfqq) { struct cfq_data *cfqd = cfqq->cfqd; struct request *rq; int fifo; if (cfq_cfqq_fifo_expire(cfqq)) return NULL; cfq_mark_cfqq_fifo_expire(cfqq); if (list_empty(&cfqq->fifo)) return NULL; fifo = cfq_cfqq_sync(cfqq); rq = rq_entry_fifo(cfqq->fifo.next); if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) return NULL; return rq; } static inline int cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) { const int base_rq = cfqd->cfq_slice_async_rq; WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio)); } /* * Select a queue for service. If we have a current active queue, * check whether to continue servicing it, or retrieve and set a new one. */ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) { struct cfq_queue *cfqq; cfqq = cfqd->active_queue; if (!cfqq) goto new_queue; /* * The active queue has run out of time, expire it and select new. */ if (cfq_slice_used(cfqq)) goto expire; /* * The active queue has requests and isn't expired, allow it to * dispatch. */ if (!RB_EMPTY_ROOT(&cfqq->sort_list)) goto keep_queue; /* * No requests pending. If the active queue still has requests in * flight or is idling for a new request, allow either of these * conditions to happen (or time out) before selecting a new queue. */ if (timer_pending(&cfqd->idle_slice_timer) || (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) { cfqq = NULL; goto keep_queue; } expire: cfq_slice_expired(cfqd, 0); new_queue: cfqq = cfq_set_active_queue(cfqd); keep_queue: return cfqq; } /* * Dispatch some requests from cfqq, moving them to the request queue * dispatch list. */ static int __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq, int max_dispatch) { int dispatched = 0; BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list)); do { struct request *rq; /* * follow expired path, else get first next available */ if ((rq = cfq_check_fifo(cfqq)) == NULL) rq = cfqq->next_rq; /* * finally, insert request into driver dispatch list */ cfq_dispatch_insert(cfqd->queue, rq); dispatched++; if (!cfqd->active_cic) { atomic_inc(&RQ_CIC(rq)->ioc->refcount); cfqd->active_cic = RQ_CIC(rq); } if (RB_EMPTY_ROOT(&cfqq->sort_list)) break; } while (dispatched < max_dispatch); /* * expire an async queue immediately if it has used up its slice. idle * queue always expire after 1 dispatch round. */ if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) && dispatched >= cfq_prio_to_maxrq(cfqd, cfqq)) || cfq_class_idle(cfqq))) { cfqq->slice_end = jiffies + 1; cfq_slice_expired(cfqd, 0); } return dispatched; } static inline int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq) { int dispatched = 0; while (cfqq->next_rq) { cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq); dispatched++; } BUG_ON(!list_empty(&cfqq->fifo)); return dispatched; } /* * Drain our current requests. Used for barriers and when switching * io schedulers on-the-fly. */ static int cfq_forced_dispatch(struct cfq_data *cfqd) { int dispatched = 0; struct rb_node *n; while ((n = cfq_rb_first(&cfqd->service_tree)) != NULL) { struct cfq_queue *cfqq = rb_entry(n, struct cfq_queue, rb_node); dispatched += __cfq_forced_dispatch_cfqq(cfqq); } cfq_slice_expired(cfqd, 0); BUG_ON(cfqd->busy_queues); return dispatched; } static int cfq_dispatch_requests(struct request_queue *q, int force) { struct cfq_data *cfqd = q->elevator->elevator_data; struct cfq_queue *cfqq; int dispatched; if (!cfqd->busy_queues) return 0; if (unlikely(force)) return cfq_forced_dispatch(cfqd); dispatched = 0; while ((cfqq = cfq_select_queue(cfqd)) != NULL) { int max_dispatch; max_dispatch = cfqd->cfq_quantum; if (cfq_class_idle(cfqq)) max_dispatch = 1; if (cfqq->dispatched >= max_dispatch) { if (cfqd->busy_queues > 1) break; if (cfqq->dispatched >= 4 * max_dispatch) break; } if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq)) break; cfq_clear_cfqq_must_dispatch(cfqq); cfq_clear_cfqq_wait_request(cfqq); del_timer(&cfqd->idle_slice_timer); dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch); } return dispatched; } /* * task holds one reference to the queue, dropped when task exits. each rq * in-flight on this queue also holds a reference, dropped when rq is freed. * * queue lock must be held here. */ static void cfq_put_queue(struct cfq_queue *cfqq) { struct cfq_data *cfqd = cfqq->cfqd; BUG_ON(atomic_read(&cfqq->ref) <= 0); if (!atomic_dec_and_test(&cfqq->ref)) return; BUG_ON(rb_first(&cfqq->sort_list)); BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]); BUG_ON(cfq_cfqq_on_rr(cfqq)); if (unlikely(cfqd->active_queue == cfqq)) { __cfq_slice_expired(cfqd, cfqq, 0); cfq_schedule_dispatch(cfqd); } kmem_cache_free(cfq_pool, cfqq); } static void cfq_free_io_context(struct io_context *ioc) { struct cfq_io_context *__cic; struct rb_node *n; int freed = 0; ioc->ioc_data = NULL; while ((n = rb_first(&ioc->cic_root)) != NULL) { __cic = rb_entry(n, struct cfq_io_context, rb_node); rb_erase(&__cic->rb_node, &ioc->cic_root); kmem_cache_free(cfq_ioc_pool, __cic); freed++; } elv_ioc_count_mod(ioc_count, -freed); if (ioc_gone && !elv_ioc_count_read(ioc_count)) complete(ioc_gone); } static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq) { if (unlikely(cfqq == cfqd->active_queue)) { __cfq_slice_expired(cfqd, cfqq, 0); cfq_schedule_dispatch(cfqd); } cfq_put_queue(cfqq); } static void __cfq_exit_single_io_context(struct cfq_data *cfqd, struct cfq_io_context *cic) { list_del_init(&cic->queue_list); smp_wmb(); cic->key = NULL; if (cic->cfqq[ASYNC]) { cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]); cic->cfqq[ASYNC] = NULL; } if (cic->cfqq[SYNC]) { cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]); cic->cfqq[SYNC] = NULL; } } static void cfq_exit_single_io_context(struct cfq_io_context *cic) { struct cfq_data *cfqd = cic->key; if (cfqd) { struct request_queue *q = cfqd->queue; spin_lock_irq(q->queue_lock); __cfq_exit_single_io_context(cfqd, cic); spin_unlock_irq(q->queue_lock); } } /* * The process that ioc belongs to has exited, we need to clean up * and put the internal structures we have that belongs to that process. */ static void cfq_exit_io_context(struct io_context *ioc) { struct cfq_io_context *__cic; struct rb_node *n; ioc->ioc_data = NULL; /* * put the reference this task is holding to the various queues */ n = rb_first(&ioc->cic_root); while (n != NULL) { __cic = rb_entry(n, struct cfq_io_context, rb_node); cfq_exit_single_io_context(__cic); n = rb_next(n); } } static struct cfq_io_context * cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) { struct cfq_io_context *cic; cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO, cfqd->queue->node); if (cic) { cic->last_end_request = jiffies; INIT_LIST_HEAD(&cic->queue_list); cic->dtor = cfq_free_io_context; cic->exit = cfq_exit_io_context; elv_ioc_count_inc(ioc_count); } return cic; } static void cfq_init_prio_data(struct cfq_queue *cfqq) { struct task_struct *tsk = current; int ioprio_class; if (!cfq_cfqq_prio_changed(cfqq)) return; ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio); switch (ioprio_class) { default: printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class); case IOPRIO_CLASS_NONE: /* * no prio set, place us in the middle of the BE classes */ cfqq->ioprio = task_nice_ioprio(tsk); cfqq->ioprio_class = IOPRIO_CLASS_BE; break; case IOPRIO_CLASS_RT: cfqq->ioprio = task_ioprio(tsk); cfqq->ioprio_class = IOPRIO_CLASS_RT; break; case IOPRIO_CLASS_BE: cfqq->ioprio = task_ioprio(tsk); cfqq->ioprio_class = IOPRIO_CLASS_BE; break; case IOPRIO_CLASS_IDLE: cfqq->ioprio_class = IOPRIO_CLASS_IDLE; cfqq->ioprio = 7; cfq_clear_cfqq_idle_window(cfqq); break; } /* * keep track of original prio settings in case we have to temporarily * elevate the priority of this queue */ cfqq->org_ioprio = cfqq->ioprio; cfqq->org_ioprio_class = cfqq->ioprio_class; cfq_clear_cfqq_prio_changed(cfqq); } static inline void changed_ioprio(struct cfq_io_context *cic) { struct cfq_data *cfqd = cic->key; struct cfq_queue *cfqq; unsigned long flags; if (unlikely(!cfqd)) return; spin_lock_irqsave(cfqd->queue->queue_lock, flags); cfqq = cic->cfqq[ASYNC]; if (cfqq) { struct cfq_queue *new_cfqq; new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc->task, GFP_ATOMIC); if (new_cfqq) { cic->cfqq[ASYNC] = new_cfqq; cfq_put_queue(cfqq); } } cfqq = cic->cfqq[SYNC]; if (cfqq) cfq_mark_cfqq_prio_changed(cfqq); spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); } static void cfq_ioc_set_ioprio(struct io_context *ioc) { struct cfq_io_context *cic; struct rb_node *n; ioc->ioprio_changed = 0; n = rb_first(&ioc->cic_root); while (n != NULL) { cic = rb_entry(n, struct cfq_io_context, rb_node); changed_ioprio(cic); n = rb_next(n); } } static struct cfq_queue * cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk, gfp_t gfp_mask) { struct cfq_queue *cfqq, *new_cfqq = NULL; struct cfq_io_context *cic; retry: cic = cfq_cic_rb_lookup(cfqd, tsk->io_context); /* cic always exists here */ cfqq = cic_to_cfqq(cic, is_sync); if (!cfqq) { if (new_cfqq) { cfqq = new_cfqq; new_cfqq = NULL; } else if (gfp_mask & __GFP_WAIT) { /* * Inform the allocator of the fact that we will * just repeat this allocation if it fails, to allow * the allocator to do whatever it needs to attempt to * free memory. */ spin_unlock_irq(cfqd->queue->queue_lock); new_cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask | __GFP_NOFAIL | __GFP_ZERO, cfqd->queue->node); spin_lock_irq(cfqd->queue->queue_lock); goto retry; } else { cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask | __GFP_ZERO, cfqd->queue->node); if (!cfqq) goto out; } RB_CLEAR_NODE(&cfqq->rb_node); INIT_LIST_HEAD(&cfqq->fifo); atomic_set(&cfqq->ref, 0); cfqq->cfqd = cfqd; if (is_sync) { cfq_mark_cfqq_idle_window(cfqq); cfq_mark_cfqq_sync(cfqq); } cfq_mark_cfqq_prio_changed(cfqq); cfq_mark_cfqq_queue_new(cfqq); cfq_init_prio_data(cfqq); } if (new_cfqq) kmem_cache_free(cfq_pool, new_cfqq); out: WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq); return cfqq; } static struct cfq_queue ** cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio) { switch(ioprio_class) { case IOPRIO_CLASS_RT: return &cfqd->async_cfqq[0][ioprio]; case IOPRIO_CLASS_BE: return &cfqd->async_cfqq[1][ioprio]; case IOPRIO_CLASS_IDLE: return &cfqd->async_idle_cfqq; default: BUG(); } } static struct cfq_queue * cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk, gfp_t gfp_mask) { const int ioprio = task_ioprio(tsk); const int ioprio_class = task_ioprio_class(tsk); struct cfq_queue **async_cfqq = NULL; struct cfq_queue *cfqq = NULL; if (!is_sync) { async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio); cfqq = *async_cfqq; } if (!cfqq) cfqq = cfq_find_alloc_queue(cfqd, is_sync, tsk, gfp_mask); /* * pin the queue now that it's allocated, scheduler exit will prune it */ if (!is_sync && !(*async_cfqq)) { atomic_inc(&cfqq->ref); *async_cfqq = cfqq; } atomic_inc(&cfqq->ref); return cfqq; } /* * We drop cfq io contexts lazily, so we may find a dead one. */ static void cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic) { WARN_ON(!list_empty(&cic->queue_list)); if (ioc->ioc_data == cic) ioc->ioc_data = NULL; rb_erase(&cic->rb_node, &ioc->cic_root); kmem_cache_free(cfq_ioc_pool, cic); elv_ioc_count_dec(ioc_count); } static struct cfq_io_context * cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc) { struct rb_node *n; struct cfq_io_context *cic; void *k, *key = cfqd; if (unlikely(!ioc)) return NULL; /* * we maintain a last-hit cache, to avoid browsing over the tree */ cic = ioc->ioc_data; if (cic && cic->key == cfqd) return cic; restart: n = ioc->cic_root.rb_node; while (n) { cic = rb_entry(n, struct cfq_io_context, rb_node); /* ->key must be copied to avoid race with cfq_exit_queue() */ k = cic->key; if (unlikely(!k)) { cfq_drop_dead_cic(ioc, cic); goto restart; } if (key < k) n = n->rb_left; else if (key > k) n = n->rb_right; else { ioc->ioc_data = cic; return cic; } } return NULL; } static inline void cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, struct cfq_io_context *cic) { struct rb_node **p; struct rb_node *parent; struct cfq_io_context *__cic; unsigned long flags; void *k; cic->ioc = ioc; cic->key = cfqd; restart: parent = NULL; p = &ioc->cic_root.rb_node; while (*p) { parent = *p; __cic = rb_entry(parent, struct cfq_io_context, rb_node); /* ->key must be copied to avoid race with cfq_exit_queue() */ k = __cic->key; if (unlikely(!k)) { cfq_drop_dead_cic(ioc, __cic); goto restart; } if (cic->key < k) p = &(*p)->rb_left; else if (cic->key > k) p = &(*p)->rb_right; else BUG(); } rb_link_node(&cic->rb_node, parent, p); rb_insert_color(&cic->rb_node, &ioc->cic_root); spin_lock_irqsave(cfqd->queue->queue_lock, flags); list_add(&cic->queue_list, &cfqd->cic_list); spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); } /* * Setup general io context and cfq io context. There can be several cfq * io contexts per general io context, if this process is doing io to more * than one device managed by cfq. */ static struct cfq_io_context * cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) { struct io_context *ioc = NULL; struct cfq_io_context *cic; might_sleep_if(gfp_mask & __GFP_WAIT); ioc = get_io_context(gfp_mask, cfqd->queue->node); if (!ioc) return NULL; cic = cfq_cic_rb_lookup(cfqd, ioc); if (cic) goto out; cic = cfq_alloc_io_context(cfqd, gfp_mask); if (cic == NULL) goto err; cfq_cic_link(cfqd, ioc, cic); out: smp_read_barrier_depends(); if (unlikely(ioc->ioprio_changed)) cfq_ioc_set_ioprio(ioc); return cic; err: put_io_context(ioc); return NULL; } static void cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic) { unsigned long elapsed = jiffies - cic->last_end_request; unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle); cic->ttime_samples = (7*cic->ttime_samples + 256) / 8; cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8; cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples; } static void cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic, struct request *rq) { sector_t sdist; u64 total; if (cic->last_request_pos < rq->sector) sdist = rq->sector - cic->last_request_pos; else sdist = cic->last_request_pos - rq->sector; /* * Don't allow the seek distance to get too large from the * odd fragment, pagein, etc */ if (cic->seek_samples <= 60) /* second&third seek */ sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024); else sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64); cic->seek_samples = (7*cic->seek_samples + 256) / 8; cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8; total = cic->seek_total + (cic->seek_samples/2); do_div(total, cic->seek_samples); cic->seek_mean = (sector_t)total; } /* * Disable idle window if the process thinks too long or seeks so much that * it doesn't matter */ static void cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, struct cfq_io_context *cic) { int enable_idle; if (!cfq_cfqq_sync(cfqq)) return; enable_idle = cfq_cfqq_idle_window(cfqq); if (!cic->ioc->task || !cfqd->cfq_slice_idle || (cfqd->hw_tag && CIC_SEEKY(cic))) enable_idle = 0; else if (sample_valid(cic->ttime_samples)) { if (cic->ttime_mean > cfqd->cfq_slice_idle) enable_idle = 0; else enable_idle = 1; } if (enable_idle) cfq_mark_cfqq_idle_window(cfqq); else cfq_clear_cfqq_idle_window(cfqq); } /* * Check if new_cfqq should preempt the currently active queue. Return 0 for * no or if we aren't sure, a 1 will cause a preempt. */ static int cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, struct request *rq) { struct cfq_queue *cfqq; cfqq = cfqd->active_queue; if (!cfqq) return 0; if (cfq_slice_used(cfqq)) return 1; if (cfq_class_idle(new_cfqq)) return 0; if (cfq_class_idle(cfqq)) return 1; /* * if the new request is sync, but the currently running queue is * not, let the sync request have priority. */ if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) return 1; /* * So both queues are sync. Let the new request get disk time if * it's a metadata request and the current queue is doing regular IO. */ if (rq_is_meta(rq) && !cfqq->meta_pending) return 1; if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) return 0; /* * if this request is as-good as one we would expect from the * current cfqq, let it preempt */ if (cfq_rq_close(cfqd, rq)) return 1; return 0; } /* * cfqq preempts the active queue. if we allowed preempt with no slice left, * let it have half of its nominal slice. */ static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) { cfq_slice_expired(cfqd, 1); /* * Put the new queue at the front of the of the current list, * so we know that it will be selected next. */ BUG_ON(!cfq_cfqq_on_rr(cfqq)); cfq_service_tree_add(cfqd, cfqq, 1); cfqq->slice_end = 0; cfq_mark_cfqq_slice_new(cfqq); } /* * Called when a new fs request (rq) is added (to cfqq). Check if there's * something we should do about it */ static void cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, struct request *rq) { struct cfq_io_context *cic = RQ_CIC(rq); if (rq_is_meta(rq)) cfqq->meta_pending++; cfq_update_io_thinktime(cfqd, cic); cfq_update_io_seektime(cfqd, cic, rq); cfq_update_idle_window(cfqd, cfqq, cic); cic->last_request_pos = rq->sector + rq->nr_sectors; if (cfqq == cfqd->active_queue) { /* * if we are waiting for a request for this queue, let it rip * immediately and flag that we must not expire this queue * just now */ if (cfq_cfqq_wait_request(cfqq)) { cfq_mark_cfqq_must_dispatch(cfqq); del_timer(&cfqd->idle_slice_timer); blk_start_queueing(cfqd->queue); } } else if (cfq_should_preempt(cfqd, cfqq, rq)) { /* * not the active queue - expire current slice if it is * idle and has expired it's mean thinktime or this new queue * has some old slice time left and is of higher priority */ cfq_preempt_queue(cfqd, cfqq); cfq_mark_cfqq_must_dispatch(cfqq); blk_start_queueing(cfqd->queue); } } static void cfq_insert_request(struct request_queue *q, struct request *rq) { struct cfq_data *cfqd = q->elevator->elevator_data; struct cfq_queue *cfqq = RQ_CFQQ(rq); cfq_init_prio_data(cfqq); cfq_add_rq_rb(rq); list_add_tail(&rq->queuelist, &cfqq->fifo); cfq_rq_enqueued(cfqd, cfqq, rq); } static void cfq_completed_request(struct request_queue *q, struct request *rq) { struct cfq_queue *cfqq = RQ_CFQQ(rq); struct cfq_data *cfqd = cfqq->cfqd; const int sync = rq_is_sync(rq); unsigned long now; now = jiffies; WARN_ON(!cfqd->rq_in_driver); WARN_ON(!cfqq->dispatched); cfqd->rq_in_driver--; cfqq->dispatched--; if (cfq_cfqq_sync(cfqq)) cfqd->sync_flight--; if (!cfq_class_idle(cfqq)) cfqd->last_end_request = now; if (sync) RQ_CIC(rq)->last_end_request = now; /* * If this is the active queue, check if it needs to be expired, * or if we want to idle in case it has no pending requests. */ if (cfqd->active_queue == cfqq) { if (cfq_cfqq_slice_new(cfqq)) { cfq_set_prio_slice(cfqd, cfqq); cfq_clear_cfqq_slice_new(cfqq); } if (cfq_slice_used(cfqq)) cfq_slice_expired(cfqd, 1); else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list)) cfq_arm_slice_timer(cfqd); } if (!cfqd->rq_in_driver) cfq_schedule_dispatch(cfqd); } /* * we temporarily boost lower priority queues if they are holding fs exclusive * resources. they are boosted to normal prio (CLASS_BE/4) */ static void cfq_prio_boost(struct cfq_queue *cfqq) { if (has_fs_excl()) { /* * boost idle prio on transactions that would lock out other * users of the filesystem */ if (cfq_class_idle(cfqq)) cfqq->ioprio_class = IOPRIO_CLASS_BE; if (cfqq->ioprio > IOPRIO_NORM) cfqq->ioprio = IOPRIO_NORM; } else { /* * check if we need to unboost the queue */ if (cfqq->ioprio_class != cfqq->org_ioprio_class) cfqq->ioprio_class = cfqq->org_ioprio_class; if (cfqq->ioprio != cfqq->org_ioprio) cfqq->ioprio = cfqq->org_ioprio; } } static inline int __cfq_may_queue(struct cfq_queue *cfqq) { if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) && !cfq_cfqq_must_alloc_slice(cfqq)) { cfq_mark_cfqq_must_alloc_slice(cfqq); return ELV_MQUEUE_MUST; } return ELV_MQUEUE_MAY; } static int cfq_may_queue(struct request_queue *q, int rw) { struct cfq_data *cfqd = q->elevator->elevator_data; struct task_struct *tsk = current; struct cfq_io_context *cic; struct cfq_queue *cfqq; /* * don't force setup of a queue from here, as a call to may_queue * does not necessarily imply that a request actually will be queued. * so just lookup a possibly existing queue, or return 'may queue' * if that fails */ cic = cfq_cic_rb_lookup(cfqd, tsk->io_context); if (!cic) return ELV_MQUEUE_MAY; cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC); if (cfqq) { cfq_init_prio_data(cfqq); cfq_prio_boost(cfqq); return __cfq_may_queue(cfqq); } return ELV_MQUEUE_MAY; } /* * queue lock held here */ static void cfq_put_request(struct request *rq) { struct cfq_queue *cfqq = RQ_CFQQ(rq); if (cfqq) { const int rw = rq_data_dir(rq); BUG_ON(!cfqq->allocated[rw]); cfqq->allocated[rw]--; put_io_context(RQ_CIC(rq)->ioc); rq->elevator_private = NULL; rq->elevator_private2 = NULL; cfq_put_queue(cfqq); } } /* * Allocate cfq data structures associated with this request. */ static int cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) { struct cfq_data *cfqd = q->elevator->elevator_data; struct task_struct *tsk = current; struct cfq_io_context *cic; const int rw = rq_data_dir(rq); const int is_sync = rq_is_sync(rq); struct cfq_queue *cfqq; unsigned long flags; might_sleep_if(gfp_mask & __GFP_WAIT); cic = cfq_get_io_context(cfqd, gfp_mask); spin_lock_irqsave(q->queue_lock, flags); if (!cic) goto queue_fail; cfqq = cic_to_cfqq(cic, is_sync); if (!cfqq) { cfqq = cfq_get_queue(cfqd, is_sync, tsk, gfp_mask); if (!cfqq) goto queue_fail; cic_set_cfqq(cic, cfqq, is_sync); } cfqq->allocated[rw]++; cfq_clear_cfqq_must_alloc(cfqq); atomic_inc(&cfqq->ref); spin_unlock_irqrestore(q->queue_lock, flags); rq->elevator_private = cic; rq->elevator_private2 = cfqq; return 0; queue_fail: if (cic) put_io_context(cic->ioc); cfq_schedule_dispatch(cfqd); spin_unlock_irqrestore(q->queue_lock, flags); return 1; } static void cfq_kick_queue(struct work_struct *work) { struct cfq_data *cfqd = container_of(work, struct cfq_data, unplug_work); struct request_queue *q = cfqd->queue; unsigned long flags; spin_lock_irqsave(q->queue_lock, flags); blk_start_queueing(q); spin_unlock_irqrestore(q->queue_lock, flags); } /* * Timer running if the active_queue is currently idling inside its time slice */ static void cfq_idle_slice_timer(unsigned long data) { struct cfq_data *cfqd = (struct cfq_data *) data; struct cfq_queue *cfqq; unsigned long flags; int timed_out = 1; spin_lock_irqsave(cfqd->queue->queue_lock, flags); if ((cfqq = cfqd->active_queue) != NULL) { timed_out = 0; /* * expired */ if (cfq_slice_used(cfqq)) goto expire; /* * only expire and reinvoke request handler, if there are * other queues with pending requests */ if (!cfqd->busy_queues) goto out_cont; /* * not expired and it has a request pending, let it dispatch */ if (!RB_EMPTY_ROOT(&cfqq->sort_list)) { cfq_mark_cfqq_must_dispatch(cfqq); goto out_kick; } } expire: cfq_slice_expired(cfqd, timed_out); out_kick: cfq_schedule_dispatch(cfqd); out_cont: spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); } /* * Timer running if an idle class queue is waiting for service */ static void cfq_idle_class_timer(unsigned long data) { struct cfq_data *cfqd = (struct cfq_data *) data; unsigned long flags, end; spin_lock_irqsave(cfqd->queue->queue_lock, flags); /* * race with a non-idle queue, reset timer */ end = cfqd->last_end_request + CFQ_IDLE_GRACE; if (!time_after_eq(jiffies, end)) mod_timer(&cfqd->idle_class_timer, end); else cfq_schedule_dispatch(cfqd); spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); } static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) { del_timer_sync(&cfqd->idle_slice_timer); del_timer_sync(&cfqd->idle_class_timer); blk_sync_queue(cfqd->queue); } static void cfq_put_async_queues(struct cfq_data *cfqd) { int i; for (i = 0; i < IOPRIO_BE_NR; i++) { if (cfqd->async_cfqq[0][i]) cfq_put_queue(cfqd->async_cfqq[0][i]); if (cfqd->async_cfqq[1][i]) cfq_put_queue(cfqd->async_cfqq[1][i]); if (cfqd->async_idle_cfqq) cfq_put_queue(cfqd->async_idle_cfqq); } } static void cfq_exit_queue(elevator_t *e) { struct cfq_data *cfqd = e->elevator_data; struct request_queue *q = cfqd->queue; cfq_shutdown_timer_wq(cfqd); spin_lock_irq(q->queue_lock); if (cfqd->active_queue) __cfq_slice_expired(cfqd, cfqd->active_queue, 0); while (!list_empty(&cfqd->cic_list)) { struct cfq_io_context *cic = list_entry(cfqd->cic_list.next, struct cfq_io_context, queue_list); __cfq_exit_single_io_context(cfqd, cic); } cfq_put_async_queues(cfqd); spin_unlock_irq(q->queue_lock); cfq_shutdown_timer_wq(cfqd); kfree(cfqd); } static void *cfq_init_queue(struct request_queue *q) { struct cfq_data *cfqd; cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node); if (!cfqd) return NULL; cfqd->service_tree = CFQ_RB_ROOT; INIT_LIST_HEAD(&cfqd->cic_list); cfqd->queue = q; init_timer(&cfqd->idle_slice_timer); cfqd->idle_slice_timer.function = cfq_idle_slice_timer; cfqd->idle_slice_timer.data = (unsigned long) cfqd; init_timer(&cfqd->idle_class_timer); cfqd->idle_class_timer.function = cfq_idle_class_timer; cfqd->idle_class_timer.data = (unsigned long) cfqd; INIT_WORK(&cfqd->unplug_work, cfq_kick_queue); cfqd->cfq_quantum = cfq_quantum; cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0]; cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1]; cfqd->cfq_back_max = cfq_back_max; cfqd->cfq_back_penalty = cfq_back_penalty; cfqd->cfq_slice[0] = cfq_slice_async; cfqd->cfq_slice[1] = cfq_slice_sync; cfqd->cfq_slice_async_rq = cfq_slice_async_rq; cfqd->cfq_slice_idle = cfq_slice_idle; return cfqd; } static void cfq_slab_kill(void) { if (cfq_pool) kmem_cache_destroy(cfq_pool); if (cfq_ioc_pool) kmem_cache_destroy(cfq_ioc_pool); } static int __init cfq_slab_setup(void) { cfq_pool = KMEM_CACHE(cfq_queue, 0); if (!cfq_pool) goto fail; cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0); if (!cfq_ioc_pool) goto fail; return 0; fail: cfq_slab_kill(); return -ENOMEM; } /* * sysfs parts below --> */ static ssize_t cfq_var_show(unsigned int var, char *page) { return sprintf(page, "%d\n", var); } static ssize_t cfq_var_store(unsigned int *var, const char *page, size_t count) { char *p = (char *) page; *var = simple_strtoul(p, &p, 10); return count; } #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ static ssize_t __FUNC(elevator_t *e, char *page) \ { \ struct cfq_data *cfqd = e->elevator_data; \ unsigned int __data = __VAR; \ if (__CONV) \ __data = jiffies_to_msecs(__data); \ return cfq_var_show(__data, (page)); \ } SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0); SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1); SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1); SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0); SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0); SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1); SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1); SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1); SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0); #undef SHOW_FUNCTION #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \ { \ struct cfq_data *cfqd = e->elevator_data; \ unsigned int __data; \ int ret = cfq_var_store(&__data, (page), count); \ if (__data < (MIN)) \ __data = (MIN); \ else if (__data > (MAX)) \ __data = (MAX); \ if (__CONV) \ *(__PTR) = msecs_to_jiffies(__data); \ else \ *(__PTR) = __data; \ return ret; \ } STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0); STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1); STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1); STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0); STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0); STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1); STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1); STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1); STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0); #undef STORE_FUNCTION #define CFQ_ATTR(name) \ __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store) static struct elv_fs_entry cfq_attrs[] = { CFQ_ATTR(quantum), CFQ_ATTR(fifo_expire_sync), CFQ_ATTR(fifo_expire_async), CFQ_ATTR(back_seek_max), CFQ_ATTR(back_seek_penalty), CFQ_ATTR(slice_sync), CFQ_ATTR(slice_async), CFQ_ATTR(slice_async_rq), CFQ_ATTR(slice_idle), __ATTR_NULL }; static struct elevator_type iosched_cfq = { .ops = { .elevator_merge_fn = cfq_merge, .elevator_merged_fn = cfq_merged_request, .elevator_merge_req_fn = cfq_merged_requests, .elevator_allow_merge_fn = cfq_allow_merge, .elevator_dispatch_fn = cfq_dispatch_requests, .elevator_add_req_fn = cfq_insert_request, .elevator_activate_req_fn = cfq_activate_request, .elevator_deactivate_req_fn = cfq_deactivate_request, .elevator_queue_empty_fn = cfq_queue_empty, .elevator_completed_req_fn = cfq_completed_request, .elevator_former_req_fn = elv_rb_former_request, .elevator_latter_req_fn = elv_rb_latter_request, .elevator_set_req_fn = cfq_set_request, .elevator_put_req_fn = cfq_put_request, .elevator_may_queue_fn = cfq_may_queue, .elevator_init_fn = cfq_init_queue, .elevator_exit_fn = cfq_exit_queue, .trim = cfq_free_io_context, }, .elevator_attrs = cfq_attrs, .elevator_name = "cfq", .elevator_owner = THIS_MODULE, }; static int __init cfq_init(void) { int ret; /* * could be 0 on HZ < 1000 setups */ if (!cfq_slice_async) cfq_slice_async = 1; if (!cfq_slice_idle) cfq_slice_idle = 1; if (cfq_slab_setup()) return -ENOMEM; ret = elv_register(&iosched_cfq); if (ret) cfq_slab_kill(); return ret; } static void __exit cfq_exit(void) { DECLARE_COMPLETION_ONSTACK(all_gone); elv_unregister(&iosched_cfq); ioc_gone = &all_gone; /* ioc_gone's update must be visible before reading ioc_count */ smp_wmb(); if (elv_ioc_count_read(ioc_count)) wait_for_completion(ioc_gone); synchronize_rcu(); cfq_slab_kill(); } module_init(cfq_init); module_exit(cfq_exit); MODULE_AUTHOR("Jens Axboe"); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");