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author | Jens Axboe <axboe@fb.com> | 2017-01-15 01:11:11 +0100 |
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committer | Jens Axboe <axboe@fb.com> | 2017-01-17 18:04:25 +0100 |
commit | 945ffb60c11dfb228130f3f2bdde961cecb76671 (patch) | |
tree | e9b9079a7acdd5d93e1b1b866d303d056acf33f7 /block/mq-deadline.c | |
parent | blk-mq-sched: add framework for MQ capable IO schedulers (diff) | |
download | linux-945ffb60c11dfb228130f3f2bdde961cecb76671.tar.xz linux-945ffb60c11dfb228130f3f2bdde961cecb76671.zip |
mq-deadline: add blk-mq adaptation of the deadline IO scheduler
This is basically identical to deadline-iosched, except it registers
as a MQ capable scheduler. This is still a single queue design.
Signed-off-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Diffstat (limited to '')
-rw-r--r-- | block/mq-deadline.c | 553 |
1 files changed, 553 insertions, 0 deletions
diff --git a/block/mq-deadline.c b/block/mq-deadline.c new file mode 100644 index 000000000000..a01986d7b6fb --- /dev/null +++ b/block/mq-deadline.c @@ -0,0 +1,553 @@ +/* + * MQ Deadline i/o scheduler - adaptation of the legacy deadline scheduler, + * for the blk-mq scheduling framework + * + * Copyright (C) 2016 Jens Axboe <axboe@kernel.dk> + */ +#include <linux/kernel.h> +#include <linux/fs.h> +#include <linux/blkdev.h> +#include <linux/blk-mq.h> +#include <linux/elevator.h> +#include <linux/bio.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/init.h> +#include <linux/compiler.h> +#include <linux/rbtree.h> +#include <linux/sbitmap.h> + +#include "blk.h" +#include "blk-mq.h" +#include "blk-mq-tag.h" +#include "blk-mq-sched.h" + +/* + * See Documentation/block/deadline-iosched.txt + */ +static const int read_expire = HZ / 2; /* max time before a read is submitted. */ +static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */ +static const int writes_starved = 2; /* max times reads can starve a write */ +static const int fifo_batch = 16; /* # of sequential requests treated as one + by the above parameters. For throughput. */ + +struct deadline_data { + /* + * run time data + */ + + /* + * requests (deadline_rq s) are present on both sort_list and fifo_list + */ + struct rb_root sort_list[2]; + struct list_head fifo_list[2]; + + /* + * next in sort order. read, write or both are NULL + */ + struct request *next_rq[2]; + unsigned int batching; /* number of sequential requests made */ + unsigned int starved; /* times reads have starved writes */ + + /* + * settings that change how the i/o scheduler behaves + */ + int fifo_expire[2]; + int fifo_batch; + int writes_starved; + int front_merges; + + spinlock_t lock; + struct list_head dispatch; +}; + +static inline struct rb_root * +deadline_rb_root(struct deadline_data *dd, struct request *rq) +{ + return &dd->sort_list[rq_data_dir(rq)]; +} + +/* + * get the request after `rq' in sector-sorted order + */ +static inline struct request * +deadline_latter_request(struct request *rq) +{ + struct rb_node *node = rb_next(&rq->rb_node); + + if (node) + return rb_entry_rq(node); + + return NULL; +} + +static void +deadline_add_rq_rb(struct deadline_data *dd, struct request *rq) +{ + struct rb_root *root = deadline_rb_root(dd, rq); + + elv_rb_add(root, rq); +} + +static inline void +deadline_del_rq_rb(struct deadline_data *dd, struct request *rq) +{ + const int data_dir = rq_data_dir(rq); + + if (dd->next_rq[data_dir] == rq) + dd->next_rq[data_dir] = deadline_latter_request(rq); + + elv_rb_del(deadline_rb_root(dd, rq), rq); +} + +/* + * remove rq from rbtree and fifo. + */ +static void deadline_remove_request(struct request_queue *q, struct request *rq) +{ + struct deadline_data *dd = q->elevator->elevator_data; + + list_del_init(&rq->queuelist); + + /* + * We might not be on the rbtree, if we are doing an insert merge + */ + if (!RB_EMPTY_NODE(&rq->rb_node)) + deadline_del_rq_rb(dd, rq); + + elv_rqhash_del(q, rq); + if (q->last_merge == rq) + q->last_merge = NULL; +} + +static void dd_request_merged(struct request_queue *q, struct request *req, + int type) +{ + struct deadline_data *dd = q->elevator->elevator_data; + + /* + * if the merge was a front merge, we need to reposition request + */ + if (type == ELEVATOR_FRONT_MERGE) { + elv_rb_del(deadline_rb_root(dd, req), req); + deadline_add_rq_rb(dd, req); + } +} + +static void dd_merged_requests(struct request_queue *q, struct request *req, + struct request *next) +{ + /* + * if next expires before rq, assign its expire time to rq + * and move into next position (next will be deleted) in fifo + */ + if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) { + if (time_before((unsigned long)next->fifo_time, + (unsigned long)req->fifo_time)) { + list_move(&req->queuelist, &next->queuelist); + req->fifo_time = next->fifo_time; + } + } + + /* + * kill knowledge of next, this one is a goner + */ + deadline_remove_request(q, next); +} + +/* + * move an entry to dispatch queue + */ +static void +deadline_move_request(struct deadline_data *dd, struct request *rq) +{ + const int data_dir = rq_data_dir(rq); + + dd->next_rq[READ] = NULL; + dd->next_rq[WRITE] = NULL; + dd->next_rq[data_dir] = deadline_latter_request(rq); + + /* + * take it off the sort and fifo list + */ + deadline_remove_request(rq->q, rq); +} + +/* + * deadline_check_fifo returns 0 if there are no expired requests on the fifo, + * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir]) + */ +static inline int deadline_check_fifo(struct deadline_data *dd, int ddir) +{ + struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next); + + /* + * rq is expired! + */ + if (time_after_eq(jiffies, (unsigned long)rq->fifo_time)) + return 1; + + return 0; +} + +/* + * deadline_dispatch_requests selects the best request according to + * read/write expire, fifo_batch, etc + */ +static struct request *__dd_dispatch_request(struct blk_mq_hw_ctx *hctx) +{ + struct deadline_data *dd = hctx->queue->elevator->elevator_data; + struct request *rq; + bool reads, writes; + int data_dir; + + if (!list_empty(&dd->dispatch)) { + rq = list_first_entry(&dd->dispatch, struct request, queuelist); + list_del_init(&rq->queuelist); + goto done; + } + + reads = !list_empty(&dd->fifo_list[READ]); + writes = !list_empty(&dd->fifo_list[WRITE]); + + /* + * batches are currently reads XOR writes + */ + if (dd->next_rq[WRITE]) + rq = dd->next_rq[WRITE]; + else + rq = dd->next_rq[READ]; + + if (rq && dd->batching < dd->fifo_batch) + /* we have a next request are still entitled to batch */ + goto dispatch_request; + + /* + * at this point we are not running a batch. select the appropriate + * data direction (read / write) + */ + + if (reads) { + BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ])); + + if (writes && (dd->starved++ >= dd->writes_starved)) + goto dispatch_writes; + + data_dir = READ; + + goto dispatch_find_request; + } + + /* + * there are either no reads or writes have been starved + */ + + if (writes) { +dispatch_writes: + BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE])); + + dd->starved = 0; + + data_dir = WRITE; + + goto dispatch_find_request; + } + + return NULL; + +dispatch_find_request: + /* + * we are not running a batch, find best request for selected data_dir + */ + if (deadline_check_fifo(dd, data_dir) || !dd->next_rq[data_dir]) { + /* + * A deadline has expired, the last request was in the other + * direction, or we have run out of higher-sectored requests. + * Start again from the request with the earliest expiry time. + */ + rq = rq_entry_fifo(dd->fifo_list[data_dir].next); + } else { + /* + * The last req was the same dir and we have a next request in + * sort order. No expired requests so continue on from here. + */ + rq = dd->next_rq[data_dir]; + } + + dd->batching = 0; + +dispatch_request: + /* + * rq is the selected appropriate request. + */ + dd->batching++; + deadline_move_request(dd, rq); +done: + rq->rq_flags |= RQF_STARTED; + return rq; +} + +static void dd_dispatch_requests(struct blk_mq_hw_ctx *hctx, + struct list_head *rq_list) +{ + struct deadline_data *dd = hctx->queue->elevator->elevator_data; + + spin_lock(&dd->lock); + blk_mq_sched_move_to_dispatch(hctx, rq_list, __dd_dispatch_request); + spin_unlock(&dd->lock); +} + +static void dd_exit_queue(struct elevator_queue *e) +{ + struct deadline_data *dd = e->elevator_data; + + BUG_ON(!list_empty(&dd->fifo_list[READ])); + BUG_ON(!list_empty(&dd->fifo_list[WRITE])); + + kfree(dd); +} + +/* + * initialize elevator private data (deadline_data). + */ +static int dd_init_queue(struct request_queue *q, struct elevator_type *e) +{ + struct deadline_data *dd; + struct elevator_queue *eq; + + eq = elevator_alloc(q, e); + if (!eq) + return -ENOMEM; + + dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node); + if (!dd) { + kobject_put(&eq->kobj); + return -ENOMEM; + } + eq->elevator_data = dd; + + INIT_LIST_HEAD(&dd->fifo_list[READ]); + INIT_LIST_HEAD(&dd->fifo_list[WRITE]); + dd->sort_list[READ] = RB_ROOT; + dd->sort_list[WRITE] = RB_ROOT; + dd->fifo_expire[READ] = read_expire; + dd->fifo_expire[WRITE] = write_expire; + dd->writes_starved = writes_starved; + dd->front_merges = 1; + dd->fifo_batch = fifo_batch; + spin_lock_init(&dd->lock); + INIT_LIST_HEAD(&dd->dispatch); + + q->elevator = eq; + return 0; +} + +static int dd_request_merge(struct request_queue *q, struct request **rq, + struct bio *bio) +{ + struct deadline_data *dd = q->elevator->elevator_data; + sector_t sector = bio_end_sector(bio); + struct request *__rq; + + if (!dd->front_merges) + return ELEVATOR_NO_MERGE; + + __rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector); + if (__rq) { + BUG_ON(sector != blk_rq_pos(__rq)); + + if (elv_bio_merge_ok(__rq, bio)) { + *rq = __rq; + return ELEVATOR_FRONT_MERGE; + } + } + + return ELEVATOR_NO_MERGE; +} + +static bool dd_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio) +{ + struct request_queue *q = hctx->queue; + struct deadline_data *dd = q->elevator->elevator_data; + int ret; + + spin_lock(&dd->lock); + ret = blk_mq_sched_try_merge(q, bio); + spin_unlock(&dd->lock); + + return ret; +} + +/* + * add rq to rbtree and fifo + */ +static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, + bool at_head) +{ + struct request_queue *q = hctx->queue; + struct deadline_data *dd = q->elevator->elevator_data; + const int data_dir = rq_data_dir(rq); + + if (blk_mq_sched_try_insert_merge(q, rq)) + return; + + blk_mq_sched_request_inserted(rq); + + if (blk_mq_sched_bypass_insert(hctx, rq)) + return; + + if (at_head || rq->cmd_type != REQ_TYPE_FS) { + if (at_head) + list_add(&rq->queuelist, &dd->dispatch); + else + list_add_tail(&rq->queuelist, &dd->dispatch); + } else { + deadline_add_rq_rb(dd, rq); + + if (rq_mergeable(rq)) { + elv_rqhash_add(q, rq); + if (!q->last_merge) + q->last_merge = rq; + } + + /* + * set expire time and add to fifo list + */ + rq->fifo_time = jiffies + dd->fifo_expire[data_dir]; + list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]); + } +} + +static void dd_insert_requests(struct blk_mq_hw_ctx *hctx, + struct list_head *list, bool at_head) +{ + struct request_queue *q = hctx->queue; + struct deadline_data *dd = q->elevator->elevator_data; + + spin_lock(&dd->lock); + while (!list_empty(list)) { + struct request *rq; + + rq = list_first_entry(list, struct request, queuelist); + list_del_init(&rq->queuelist); + dd_insert_request(hctx, rq, at_head); + } + spin_unlock(&dd->lock); +} + +static bool dd_has_work(struct blk_mq_hw_ctx *hctx) +{ + struct deadline_data *dd = hctx->queue->elevator->elevator_data; + + return !list_empty_careful(&dd->dispatch) || + !list_empty_careful(&dd->fifo_list[0]) || + !list_empty_careful(&dd->fifo_list[1]); +} + +/* + * sysfs parts below + */ +static ssize_t +deadline_var_show(int var, char *page) +{ + return sprintf(page, "%d\n", var); +} + +static ssize_t +deadline_var_store(int *var, const char *page, size_t count) +{ + char *p = (char *) page; + + *var = simple_strtol(p, &p, 10); + return count; +} + +#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, char *page) \ +{ \ + struct deadline_data *dd = e->elevator_data; \ + int __data = __VAR; \ + if (__CONV) \ + __data = jiffies_to_msecs(__data); \ + return deadline_var_show(__data, (page)); \ +} +SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1); +SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1); +SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0); +SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0); +SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0); +#undef SHOW_FUNCTION + +#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ +{ \ + struct deadline_data *dd = e->elevator_data; \ + int __data; \ + int ret = deadline_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(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1); +STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1); +STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0); +STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0); +STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0); +#undef STORE_FUNCTION + +#define DD_ATTR(name) \ + __ATTR(name, S_IRUGO|S_IWUSR, deadline_##name##_show, \ + deadline_##name##_store) + +static struct elv_fs_entry deadline_attrs[] = { + DD_ATTR(read_expire), + DD_ATTR(write_expire), + DD_ATTR(writes_starved), + DD_ATTR(front_merges), + DD_ATTR(fifo_batch), + __ATTR_NULL +}; + +static struct elevator_type mq_deadline = { + .ops.mq = { + .insert_requests = dd_insert_requests, + .dispatch_requests = dd_dispatch_requests, + .next_request = elv_rb_latter_request, + .former_request = elv_rb_former_request, + .bio_merge = dd_bio_merge, + .request_merge = dd_request_merge, + .requests_merged = dd_merged_requests, + .request_merged = dd_request_merged, + .has_work = dd_has_work, + .init_sched = dd_init_queue, + .exit_sched = dd_exit_queue, + }, + + .uses_mq = true, + .elevator_attrs = deadline_attrs, + .elevator_name = "mq-deadline", + .elevator_owner = THIS_MODULE, +}; + +static int __init deadline_init(void) +{ + return elv_register(&mq_deadline); +} + +static void __exit deadline_exit(void) +{ + elv_unregister(&mq_deadline); +} + +module_init(deadline_init); +module_exit(deadline_exit); + +MODULE_AUTHOR("Jens Axboe"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("MQ deadline IO scheduler"); |