diff options
Diffstat (limited to 'block')
| -rw-r--r-- | block/cfq-iosched.c | 66 |
1 files changed, 50 insertions, 16 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 6a6a5f7930d..29284fa06e6 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -222,7 +222,7 @@ CFQ_CFQQ_FNS(slice_new); static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short); static void cfq_dispatch_insert(request_queue_t *, struct request *); -static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask); +static struct cfq_queue *cfq_get_queue(struct cfq_data *, unsigned int, struct task_struct *, gfp_t); /* * scheduler run of queue, if there are requests pending and no one in the @@ -389,6 +389,9 @@ cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2) } } +/* + * The below is leftmost cache rbtree addon + */ static struct rb_node *cfq_rb_first(struct cfq_rb_root *root) { if (!root->left) @@ -442,13 +445,18 @@ static unsigned long cfq_slice_offset(struct cfq_data *cfqd, return ((cfqd->busy_queues - 1) * cfq_prio_slice(cfqd, 1, 0)); } +/* + * 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) { struct rb_node **p = &cfqd->service_tree.rb.rb_node; struct rb_node *parent = NULL; unsigned long rb_key; - int left = 1; + int left; rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; rb_key += cfqq->slice_resid; @@ -464,6 +472,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); } + left = 1; while (*p) { struct cfq_queue *__cfqq; struct rb_node **n; @@ -503,17 +512,16 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, 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_queue *cfqq, int preempted) { - struct cfq_data *cfqd = cfqq->cfqd; - /* * Resorting requires the cfqq to be on the RR list already. */ - if (!cfq_cfqq_on_rr(cfqq)) - return; - - cfq_service_tree_add(cfqd, cfqq); + if (cfq_cfqq_on_rr(cfqq)) + cfq_service_tree_add(cfqq->cfqd, cfqq); } /* @@ -530,6 +538,10 @@ cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) cfq_resort_rr_list(cfqq, 0); } +/* + * 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) { @@ -654,8 +666,7 @@ static void cfq_remove_request(struct request *rq) } } -static int -cfq_merge(request_queue_t *q, struct request **req, struct bio *bio) +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; @@ -781,6 +792,10 @@ static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted, __cfq_slice_expired(cfqd, cfqq, preempted, 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 = NULL; @@ -792,10 +807,11 @@ static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) cfqq = list_entry_cfqq(cfqd->cur_rr.next); } else if (!RB_EMPTY_ROOT(&cfqd->service_tree.rb)) { struct rb_node *n = cfq_rb_first(&cfqd->service_tree); - unsigned long end; 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 @@ -813,6 +829,9 @@ static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) 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; @@ -898,6 +917,9 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd) mod_timer(&cfqd->idle_slice_timer, jiffies + sl); } +/* + * Move request from internal lists to the request queue dispatch list. + */ static void cfq_dispatch_insert(request_queue_t *q, struct request *rq) { struct cfq_queue *cfqq = RQ_CFQQ(rq); @@ -944,7 +966,8 @@ cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) } /* - * get next queue for service + * 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) { @@ -985,6 +1008,10 @@ 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) @@ -1059,6 +1086,10 @@ static int cfq_forced_dispatch_cfqqs(struct list_head *list) 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; @@ -1224,10 +1255,6 @@ static void __cfq_exit_single_io_context(struct cfq_data *cfqd, } } - -/* - * Called with interrupts disabled - */ static void cfq_exit_single_io_context(struct cfq_io_context *cic) { struct cfq_data *cfqd = cic->key; @@ -1241,6 +1268,10 @@ static void cfq_exit_single_io_context(struct cfq_io_context *cic) } } +/* + * 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; @@ -1427,6 +1458,9 @@ out: 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) { |