linux/block/mq-deadline.c

798 lines
20 KiB
C

/*
* 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-debugfs.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;
spinlock_t zone_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,
enum elv_merge 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;
}
/*
* For the specified data direction, return the next request to
* dispatch using arrival ordered lists.
*/
static struct request *
deadline_fifo_request(struct deadline_data *dd, int data_dir)
{
struct request *rq;
unsigned long flags;
if (WARN_ON_ONCE(data_dir != READ && data_dir != WRITE))
return NULL;
if (list_empty(&dd->fifo_list[data_dir]))
return NULL;
rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
if (data_dir == READ || !blk_queue_is_zoned(rq->q))
return rq;
/*
* Look for a write request that can be dispatched, that is one with
* an unlocked target zone.
*/
spin_lock_irqsave(&dd->zone_lock, flags);
list_for_each_entry(rq, &dd->fifo_list[WRITE], queuelist) {
if (blk_req_can_dispatch_to_zone(rq))
goto out;
}
rq = NULL;
out:
spin_unlock_irqrestore(&dd->zone_lock, flags);
return rq;
}
/*
* For the specified data direction, return the next request to
* dispatch using sector position sorted lists.
*/
static struct request *
deadline_next_request(struct deadline_data *dd, int data_dir)
{
struct request *rq;
unsigned long flags;
if (WARN_ON_ONCE(data_dir != READ && data_dir != WRITE))
return NULL;
rq = dd->next_rq[data_dir];
if (!rq)
return NULL;
if (data_dir == READ || !blk_queue_is_zoned(rq->q))
return rq;
/*
* Look for a write request that can be dispatched, that is one with
* an unlocked target zone.
*/
spin_lock_irqsave(&dd->zone_lock, flags);
while (rq) {
if (blk_req_can_dispatch_to_zone(rq))
break;
rq = deadline_latter_request(rq);
}
spin_unlock_irqrestore(&dd->zone_lock, flags);
return rq;
}
/*
* deadline_dispatch_requests selects the best request according to
* read/write expire, fifo_batch, etc
*/
static struct request *__dd_dispatch_request(struct deadline_data *dd)
{
struct request *rq, *next_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
*/
rq = deadline_next_request(dd, WRITE);
if (!rq)
rq = deadline_next_request(dd, 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 (deadline_fifo_request(dd, WRITE) &&
(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
*/
next_rq = deadline_next_request(dd, data_dir);
if (deadline_check_fifo(dd, data_dir) || !next_rq) {
/*
* 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 = deadline_fifo_request(dd, data_dir);
} 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 = next_rq;
}
/*
* For a zoned block device, if we only have writes queued and none of
* them can be dispatched, rq will be NULL.
*/
if (!rq)
return NULL;
dd->batching = 0;
dispatch_request:
/*
* rq is the selected appropriate request.
*/
dd->batching++;
deadline_move_request(dd, rq);
done:
/*
* If the request needs its target zone locked, do it.
*/
blk_req_zone_write_lock(rq);
rq->rq_flags |= RQF_STARTED;
return rq;
}
/*
* One confusing aspect here is that we get called for a specific
* hardware queue, but we return a request that may not be for a
* different hardware queue. This is because mq-deadline has shared
* state for all hardware queues, in terms of sorting, FIFOs, 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;
spin_lock(&dd->lock);
rq = __dd_dispatch_request(dd);
spin_unlock(&dd->lock);
return rq;
}
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);
spin_lock_init(&dd->zone_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;
struct request *free = NULL;
bool ret;
spin_lock(&dd->lock);
ret = blk_mq_sched_try_merge(q, bio, &free);
spin_unlock(&dd->lock);
if (free)
blk_mq_free_request(free);
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);
/*
* This may be a requeue of a write request that has locked its
* target zone. If it is the case, this releases the zone lock.
*/
blk_req_zone_write_unlock(rq);
if (blk_mq_sched_try_insert_merge(q, rq))
return;
blk_mq_sched_request_inserted(rq);
if (at_head || blk_rq_is_passthrough(rq)) {
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);
}
/*
* For zoned block devices, write unlock the target zone of
* completed write requests. Do this while holding the zone lock
* spinlock so that the zone is never unlocked while deadline_fifo_request()
* while deadline_next_request() are executing.
*/
static void dd_completed_request(struct request *rq)
{
struct request_queue *q = rq->q;
if (blk_queue_is_zoned(q)) {
struct deadline_data *dd = q->elevator->elevator_data;
unsigned long flags;
spin_lock_irqsave(&dd->zone_lock, flags);
blk_req_zone_write_unlock(rq);
spin_unlock_irqrestore(&dd->zone_lock, flags);
}
}
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 void
deadline_var_store(int *var, const char *page)
{
char *p = (char *) page;
*var = simple_strtol(p, &p, 10);
}
#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; \
deadline_var_store(&__data, (page)); \
if (__data < (MIN)) \
__data = (MIN); \
else if (__data > (MAX)) \
__data = (MAX); \
if (__CONV) \
*(__PTR) = msecs_to_jiffies(__data); \
else \
*(__PTR) = __data; \
return count; \
}
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
};
#ifdef CONFIG_BLK_DEBUG_FS
#define DEADLINE_DEBUGFS_DDIR_ATTRS(ddir, name) \
static void *deadline_##name##_fifo_start(struct seq_file *m, \
loff_t *pos) \
__acquires(&dd->lock) \
{ \
struct request_queue *q = m->private; \
struct deadline_data *dd = q->elevator->elevator_data; \
\
spin_lock(&dd->lock); \
return seq_list_start(&dd->fifo_list[ddir], *pos); \
} \
\
static void *deadline_##name##_fifo_next(struct seq_file *m, void *v, \
loff_t *pos) \
{ \
struct request_queue *q = m->private; \
struct deadline_data *dd = q->elevator->elevator_data; \
\
return seq_list_next(v, &dd->fifo_list[ddir], pos); \
} \
\
static void deadline_##name##_fifo_stop(struct seq_file *m, void *v) \
__releases(&dd->lock) \
{ \
struct request_queue *q = m->private; \
struct deadline_data *dd = q->elevator->elevator_data; \
\
spin_unlock(&dd->lock); \
} \
\
static const struct seq_operations deadline_##name##_fifo_seq_ops = { \
.start = deadline_##name##_fifo_start, \
.next = deadline_##name##_fifo_next, \
.stop = deadline_##name##_fifo_stop, \
.show = blk_mq_debugfs_rq_show, \
}; \
\
static int deadline_##name##_next_rq_show(void *data, \
struct seq_file *m) \
{ \
struct request_queue *q = data; \
struct deadline_data *dd = q->elevator->elevator_data; \
struct request *rq = dd->next_rq[ddir]; \
\
if (rq) \
__blk_mq_debugfs_rq_show(m, rq); \
return 0; \
}
DEADLINE_DEBUGFS_DDIR_ATTRS(READ, read)
DEADLINE_DEBUGFS_DDIR_ATTRS(WRITE, write)
#undef DEADLINE_DEBUGFS_DDIR_ATTRS
static int deadline_batching_show(void *data, struct seq_file *m)
{
struct request_queue *q = data;
struct deadline_data *dd = q->elevator->elevator_data;
seq_printf(m, "%u\n", dd->batching);
return 0;
}
static int deadline_starved_show(void *data, struct seq_file *m)
{
struct request_queue *q = data;
struct deadline_data *dd = q->elevator->elevator_data;
seq_printf(m, "%u\n", dd->starved);
return 0;
}
static void *deadline_dispatch_start(struct seq_file *m, loff_t *pos)
__acquires(&dd->lock)
{
struct request_queue *q = m->private;
struct deadline_data *dd = q->elevator->elevator_data;
spin_lock(&dd->lock);
return seq_list_start(&dd->dispatch, *pos);
}
static void *deadline_dispatch_next(struct seq_file *m, void *v, loff_t *pos)
{
struct request_queue *q = m->private;
struct deadline_data *dd = q->elevator->elevator_data;
return seq_list_next(v, &dd->dispatch, pos);
}
static void deadline_dispatch_stop(struct seq_file *m, void *v)
__releases(&dd->lock)
{
struct request_queue *q = m->private;
struct deadline_data *dd = q->elevator->elevator_data;
spin_unlock(&dd->lock);
}
static const struct seq_operations deadline_dispatch_seq_ops = {
.start = deadline_dispatch_start,
.next = deadline_dispatch_next,
.stop = deadline_dispatch_stop,
.show = blk_mq_debugfs_rq_show,
};
#define DEADLINE_QUEUE_DDIR_ATTRS(name) \
{#name "_fifo_list", 0400, .seq_ops = &deadline_##name##_fifo_seq_ops}, \
{#name "_next_rq", 0400, deadline_##name##_next_rq_show}
static const struct blk_mq_debugfs_attr deadline_queue_debugfs_attrs[] = {
DEADLINE_QUEUE_DDIR_ATTRS(read),
DEADLINE_QUEUE_DDIR_ATTRS(write),
{"batching", 0400, deadline_batching_show},
{"starved", 0400, deadline_starved_show},
{"dispatch", 0400, .seq_ops = &deadline_dispatch_seq_ops},
{},
};
#undef DEADLINE_QUEUE_DDIR_ATTRS
#endif
static struct elevator_type mq_deadline = {
.ops.mq = {
.insert_requests = dd_insert_requests,
.dispatch_request = dd_dispatch_request,
.completed_request = dd_completed_request,
.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,
#ifdef CONFIG_BLK_DEBUG_FS
.queue_debugfs_attrs = deadline_queue_debugfs_attrs,
#endif
.elevator_attrs = deadline_attrs,
.elevator_name = "mq-deadline",
.elevator_alias = "deadline",
.elevator_owner = THIS_MODULE,
};
MODULE_ALIAS("mq-deadline-iosched");
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");