cregit-Linux how code gets into the kernel

Release 4.11 block/deadline-iosched.c

Directory: block
/*
 *  Deadline i/o scheduler.
 *
 *  Copyright (C) 2002 Jens Axboe <axboe@kernel.dk>
 */
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/blkdev.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>

/*
 * 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;
};

static void deadline_move_request(struct deadline_data *, struct request *);


static inline struct rb_root * deadline_rb_root(struct deadline_data *dd, struct request *rq) { return &dd->sort_list[rq_data_dir(rq)]; }

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Aaron Carroll2683.87%133.33%
Jens Axboe516.13%266.67%
Total31100.00%3100.00%

/* * 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; }

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Aaron Carroll40100.00%1100.00%
Total40100.00%1100.00%


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); }

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PersonTokensPropCommitsCommitProp
Jens Axboe3497.14%583.33%
Aaron Carroll12.86%116.67%
Total35100.00%6100.00%


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); }

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PersonTokensPropCommitsCommitProp
Jens Axboe5895.08%571.43%
Aaron Carroll34.92%228.57%
Total61100.00%7100.00%

/* * add rq to rbtree and fifo */
static void deadline_add_request(struct request_queue *q, struct request *rq) { struct deadline_data *dd = q->elevator->elevator_data; const int data_dir = rq_data_dir(rq); deadline_add_rq_rb(dd, 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]); }

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PersonTokensPropCommitsCommitProp
Jens Axboe5271.23%666.67%
Andrew Morton1723.29%111.11%
Jan Kara34.11%111.11%
Aaron Carroll11.37%111.11%
Total73100.00%9100.00%

/* * 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; rq_fifo_clear(rq); deadline_del_rq_rb(dd, rq); }

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PersonTokensPropCommitsCommitProp
Jens Axboe3794.87%571.43%
Tejun Heo12.56%114.29%
Andrew Morton12.56%114.29%
Total39100.00%7100.00%


static enum elv_merge deadline_merge(struct request_queue *q, struct request **req, struct bio *bio) { struct deadline_data *dd = q->elevator->elevator_data; struct request *__rq; /* * check for front merge */ if (dd->front_merges) { sector_t sector = bio_end_sector(bio); __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)) { *req = __rq; return ELEVATOR_FRONT_MERGE; } } } return ELEVATOR_NO_MERGE; }

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PersonTokensPropCommitsCommitProp
Jens Axboe9988.39%763.64%
Christoph Hellwig87.14%19.09%
Tejun Heo32.68%19.09%
Tahsin Erdogan10.89%19.09%
Kent Overstreet10.89%19.09%
Total112100.00%11100.00%


static void deadline_merged_request(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); } }

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PersonTokensPropCommitsCommitProp
Jens Axboe5694.92%675.00%
Christoph Hellwig23.39%112.50%
Aaron Carroll11.69%112.50%
Total59100.00%8100.00%


static void deadline_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); }

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PersonTokensPropCommitsCommitProp
Jens Axboe7982.29%466.67%
Jan Kara1717.71%233.33%
Total96100.00%6100.00%

/* * move request from sort list to dispatch queue. */
static inline void deadline_move_to_dispatch(struct deadline_data *dd, struct request *rq) { struct request_queue *q = rq->q; deadline_remove_request(q, rq); elv_dispatch_add_tail(q, rq); }

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PersonTokensPropCommitsCommitProp
Jens Axboe40100.00%7100.00%
Total40100.00%7100.00%

/* * 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, move * to dispatch queue */ deadline_move_to_dispatch(dd, rq); }

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PersonTokensPropCommitsCommitProp
Jens Axboe6196.83%480.00%
Aaron Carroll23.17%120.00%
Total63100.00%5100.00%

/* * 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; }

Contributors

PersonTokensPropCommitsCommitProp
Jens Axboe4787.04%350.00%
Jan Kara611.11%233.33%
Xiaobing Tu11.85%116.67%
Total54100.00%6100.00%

/* * deadline_dispatch_requests selects the best request according to * read/write expire, fifo_batch, etc */
static int deadline_dispatch_requests(struct request_queue *q, int force) { struct deadline_data *dd = q->elevator->elevator_data; const int reads = !list_empty(&dd->fifo_list[READ]); const int writes = !list_empty(&dd->fifo_list[WRITE]); struct request *rq; int data_dir; /* * 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 0; 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); return 1; }

Contributors

PersonTokensPropCommitsCommitProp
Jens Axboe23888.48%654.55%
Aaron Carroll197.06%327.27%
Andrew Morton114.09%19.09%
Nikita Danilov10.37%19.09%
Total269100.00%11100.00%


static void deadline_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); }

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Jens Axboe55100.00%3100.00%
Total55100.00%3100.00%

/* * initialize elevator private data (deadline_data). */
static int deadline_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_irq(q->queue_lock); q->elevator = eq; spin_unlock_irq(q->queue_lock); return 0; }

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Jens Axboe11160.00%450.00%
Jianpeng Ma (马建朋)5931.89%112.50%
Tejun Heo105.41%112.50%
Christoph Lameter42.16%112.50%
Joe Perches10.54%112.50%
Total185100.00%8100.00%

/* * sysfs parts below */
static ssize_t deadline_var_show(int var, char *page) { return sprintf(page, "%d\n", var); }

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Jens Axboe23100.00%1100.00%
Total23100.00%1100.00%


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; }

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Jens Axboe3988.64%133.33%
Patrick Mochel49.09%133.33%
Jürgen Quade12.27%133.33%
Total44100.00%3100.00%

#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 iosched_deadline = { .ops.sq = { .elevator_merge_fn = deadline_merge, .elevator_merged_fn = deadline_merged_request, .elevator_merge_req_fn = deadline_merged_requests, .elevator_dispatch_fn = deadline_dispatch_requests, .elevator_add_req_fn = deadline_add_request, .elevator_former_req_fn = elv_rb_former_request, .elevator_latter_req_fn = elv_rb_latter_request, .elevator_init_fn = deadline_init_queue, .elevator_exit_fn = deadline_exit_queue, }, .elevator_attrs = deadline_attrs, .elevator_name = "deadline", .elevator_owner = THIS_MODULE, };
static int __init deadline_init(void) { return elv_register(&iosched_deadline); }

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Jens Axboe1593.75%266.67%
Tejun Heo16.25%133.33%
Total16100.00%3100.00%


static void __exit deadline_exit(void) { elv_unregister(&iosched_deadline); }

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Jens Axboe15100.00%3100.00%
Total15100.00%3100.00%

module_init(deadline_init); module_exit(deadline_exit); MODULE_AUTHOR("Jens Axboe"); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("deadline IO scheduler");

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Jens Axboe147783.02%2141.18%
Aaron Carroll955.34%59.80%
Jianpeng Ma (马建朋)593.32%11.96%
Al Viro432.42%23.92%
Andrew Morton301.69%47.84%
Jan Kara261.46%23.92%
Tejun Heo150.84%47.84%
Christoph Hellwig100.56%11.96%
Bernardo Innocenti50.28%11.96%
Patrick Mochel40.22%11.96%
Christoph Lameter40.22%11.96%
Arjan van de Ven40.22%11.96%
Adrian Bunk10.06%11.96%
Joe Perches10.06%11.96%
Tahsin Erdogan10.06%11.96%
Kent Overstreet10.06%11.96%
Xiaobing Tu10.06%11.96%
Jürgen Quade10.06%11.96%
Nikita Danilov10.06%11.96%
Total1779100.00%51100.00%
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