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ef9be1d336
Unlike other ioscheds, as-iosched handles alias by chaing them using rq->queuelist. As aliased requests are very rare in the first place, this complicates merge/dispatch handling without meaningful performance improvement. This patch updates as-iosched to dump aliased requests into dispatch queue as other ioscheds do. Signed-off-by: Tejun Heo <htejun@gmail.com> Signed-off-by: Jens Axboe <axboe@suse.de>
1906 lines
47 KiB
C
1906 lines
47 KiB
C
/*
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* Anticipatory & deadline i/o scheduler.
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*
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* Copyright (C) 2002 Jens Axboe <axboe@suse.de>
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* Nick Piggin <nickpiggin@yahoo.com.au>
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*
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*/
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#include <linux/kernel.h>
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#include <linux/fs.h>
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#include <linux/blkdev.h>
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#include <linux/elevator.h>
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#include <linux/bio.h>
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#include <linux/config.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/compiler.h>
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#include <linux/hash.h>
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#include <linux/rbtree.h>
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#include <linux/interrupt.h>
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#define REQ_SYNC 1
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#define REQ_ASYNC 0
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/*
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* See Documentation/block/as-iosched.txt
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*/
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/*
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* max time before a read is submitted.
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*/
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#define default_read_expire (HZ / 8)
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/*
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* ditto for writes, these limits are not hard, even
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* if the disk is capable of satisfying them.
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*/
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#define default_write_expire (HZ / 4)
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/*
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* read_batch_expire describes how long we will allow a stream of reads to
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* persist before looking to see whether it is time to switch over to writes.
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*/
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#define default_read_batch_expire (HZ / 2)
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/*
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* write_batch_expire describes how long we want a stream of writes to run for.
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* This is not a hard limit, but a target we set for the auto-tuning thingy.
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* See, the problem is: we can send a lot of writes to disk cache / TCQ in
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* a short amount of time...
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*/
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#define default_write_batch_expire (HZ / 8)
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/*
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* max time we may wait to anticipate a read (default around 6ms)
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*/
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#define default_antic_expire ((HZ / 150) ? HZ / 150 : 1)
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/*
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* Keep track of up to 20ms thinktimes. We can go as big as we like here,
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* however huge values tend to interfere and not decay fast enough. A program
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* might be in a non-io phase of operation. Waiting on user input for example,
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* or doing a lengthy computation. A small penalty can be justified there, and
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* will still catch out those processes that constantly have large thinktimes.
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*/
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#define MAX_THINKTIME (HZ/50UL)
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/* Bits in as_io_context.state */
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enum as_io_states {
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AS_TASK_RUNNING=0, /* Process has not exited */
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AS_TASK_IOSTARTED, /* Process has started some IO */
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AS_TASK_IORUNNING, /* Process has completed some IO */
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};
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enum anticipation_status {
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ANTIC_OFF=0, /* Not anticipating (normal operation) */
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ANTIC_WAIT_REQ, /* The last read has not yet completed */
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ANTIC_WAIT_NEXT, /* Currently anticipating a request vs
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last read (which has completed) */
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ANTIC_FINISHED, /* Anticipating but have found a candidate
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* or timed out */
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};
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struct as_data {
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/*
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* run time data
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*/
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struct request_queue *q; /* the "owner" queue */
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/*
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* requests (as_rq s) are present on both sort_list and fifo_list
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*/
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struct rb_root sort_list[2];
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struct list_head fifo_list[2];
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struct as_rq *next_arq[2]; /* next in sort order */
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sector_t last_sector[2]; /* last REQ_SYNC & REQ_ASYNC sectors */
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struct list_head *hash; /* request hash */
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unsigned long exit_prob; /* probability a task will exit while
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being waited on */
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unsigned long exit_no_coop; /* probablility an exited task will
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not be part of a later cooperating
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request */
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unsigned long new_ttime_total; /* mean thinktime on new proc */
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unsigned long new_ttime_mean;
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u64 new_seek_total; /* mean seek on new proc */
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sector_t new_seek_mean;
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unsigned long current_batch_expires;
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unsigned long last_check_fifo[2];
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int changed_batch; /* 1: waiting for old batch to end */
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int new_batch; /* 1: waiting on first read complete */
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int batch_data_dir; /* current batch REQ_SYNC / REQ_ASYNC */
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int write_batch_count; /* max # of reqs in a write batch */
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int current_write_count; /* how many requests left this batch */
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int write_batch_idled; /* has the write batch gone idle? */
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mempool_t *arq_pool;
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enum anticipation_status antic_status;
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unsigned long antic_start; /* jiffies: when it started */
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struct timer_list antic_timer; /* anticipatory scheduling timer */
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struct work_struct antic_work; /* Deferred unplugging */
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struct io_context *io_context; /* Identify the expected process */
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int ioc_finished; /* IO associated with io_context is finished */
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int nr_dispatched;
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/*
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* settings that change how the i/o scheduler behaves
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*/
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unsigned long fifo_expire[2];
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unsigned long batch_expire[2];
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unsigned long antic_expire;
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};
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#define list_entry_fifo(ptr) list_entry((ptr), struct as_rq, fifo)
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/*
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* per-request data.
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*/
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enum arq_state {
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AS_RQ_NEW=0, /* New - not referenced and not on any lists */
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AS_RQ_QUEUED, /* In the request queue. It belongs to the
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scheduler */
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AS_RQ_DISPATCHED, /* On the dispatch list. It belongs to the
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driver now */
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AS_RQ_PRESCHED, /* Debug poisoning for requests being used */
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AS_RQ_REMOVED,
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AS_RQ_MERGED,
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AS_RQ_POSTSCHED, /* when they shouldn't be */
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};
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struct as_rq {
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/*
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* rbtree index, key is the starting offset
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*/
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struct rb_node rb_node;
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sector_t rb_key;
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struct request *request;
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struct io_context *io_context; /* The submitting task */
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/*
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* request hash, key is the ending offset (for back merge lookup)
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*/
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struct list_head hash;
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unsigned int on_hash;
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/*
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* expire fifo
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*/
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struct list_head fifo;
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unsigned long expires;
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unsigned int is_sync;
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enum arq_state state;
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};
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#define RQ_DATA(rq) ((struct as_rq *) (rq)->elevator_private)
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static kmem_cache_t *arq_pool;
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static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq);
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static void as_antic_stop(struct as_data *ad);
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/*
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* IO Context helper functions
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*/
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/* Called to deallocate the as_io_context */
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static void free_as_io_context(struct as_io_context *aic)
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{
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kfree(aic);
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}
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/* Called when the task exits */
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static void exit_as_io_context(struct as_io_context *aic)
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{
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WARN_ON(!test_bit(AS_TASK_RUNNING, &aic->state));
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clear_bit(AS_TASK_RUNNING, &aic->state);
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}
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static struct as_io_context *alloc_as_io_context(void)
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{
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struct as_io_context *ret;
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ret = kmalloc(sizeof(*ret), GFP_ATOMIC);
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if (ret) {
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ret->dtor = free_as_io_context;
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ret->exit = exit_as_io_context;
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ret->state = 1 << AS_TASK_RUNNING;
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atomic_set(&ret->nr_queued, 0);
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atomic_set(&ret->nr_dispatched, 0);
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spin_lock_init(&ret->lock);
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ret->ttime_total = 0;
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ret->ttime_samples = 0;
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ret->ttime_mean = 0;
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ret->seek_total = 0;
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ret->seek_samples = 0;
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ret->seek_mean = 0;
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}
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return ret;
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}
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/*
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* If the current task has no AS IO context then create one and initialise it.
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* Then take a ref on the task's io context and return it.
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*/
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static struct io_context *as_get_io_context(void)
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{
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struct io_context *ioc = get_io_context(GFP_ATOMIC);
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if (ioc && !ioc->aic) {
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ioc->aic = alloc_as_io_context();
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if (!ioc->aic) {
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put_io_context(ioc);
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ioc = NULL;
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}
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}
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return ioc;
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}
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static void as_put_io_context(struct as_rq *arq)
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{
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struct as_io_context *aic;
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if (unlikely(!arq->io_context))
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return;
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aic = arq->io_context->aic;
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if (arq->is_sync == REQ_SYNC && aic) {
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spin_lock(&aic->lock);
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set_bit(AS_TASK_IORUNNING, &aic->state);
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aic->last_end_request = jiffies;
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spin_unlock(&aic->lock);
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}
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put_io_context(arq->io_context);
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}
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/*
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* the back merge hash support functions
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*/
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static const int as_hash_shift = 6;
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#define AS_HASH_BLOCK(sec) ((sec) >> 3)
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#define AS_HASH_FN(sec) (hash_long(AS_HASH_BLOCK((sec)), as_hash_shift))
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#define AS_HASH_ENTRIES (1 << as_hash_shift)
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#define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors)
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#define list_entry_hash(ptr) list_entry((ptr), struct as_rq, hash)
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static inline void __as_del_arq_hash(struct as_rq *arq)
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{
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arq->on_hash = 0;
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list_del_init(&arq->hash);
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}
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static inline void as_del_arq_hash(struct as_rq *arq)
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{
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if (arq->on_hash)
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__as_del_arq_hash(arq);
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}
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static void as_add_arq_hash(struct as_data *ad, struct as_rq *arq)
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{
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struct request *rq = arq->request;
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BUG_ON(arq->on_hash);
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arq->on_hash = 1;
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list_add(&arq->hash, &ad->hash[AS_HASH_FN(rq_hash_key(rq))]);
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}
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/*
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* move hot entry to front of chain
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*/
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static inline void as_hot_arq_hash(struct as_data *ad, struct as_rq *arq)
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{
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struct request *rq = arq->request;
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struct list_head *head = &ad->hash[AS_HASH_FN(rq_hash_key(rq))];
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if (!arq->on_hash) {
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WARN_ON(1);
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return;
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}
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if (arq->hash.prev != head) {
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list_del(&arq->hash);
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list_add(&arq->hash, head);
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}
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}
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static struct request *as_find_arq_hash(struct as_data *ad, sector_t offset)
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{
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struct list_head *hash_list = &ad->hash[AS_HASH_FN(offset)];
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struct list_head *entry, *next = hash_list->next;
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while ((entry = next) != hash_list) {
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struct as_rq *arq = list_entry_hash(entry);
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struct request *__rq = arq->request;
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next = entry->next;
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BUG_ON(!arq->on_hash);
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if (!rq_mergeable(__rq)) {
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as_del_arq_hash(arq);
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continue;
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}
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if (rq_hash_key(__rq) == offset)
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return __rq;
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}
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return NULL;
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}
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/*
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* rb tree support functions
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*/
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#define RB_NONE (2)
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#define RB_EMPTY(root) ((root)->rb_node == NULL)
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#define ON_RB(node) ((node)->rb_color != RB_NONE)
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#define RB_CLEAR(node) ((node)->rb_color = RB_NONE)
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#define rb_entry_arq(node) rb_entry((node), struct as_rq, rb_node)
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#define ARQ_RB_ROOT(ad, arq) (&(ad)->sort_list[(arq)->is_sync])
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#define rq_rb_key(rq) (rq)->sector
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/*
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* as_find_first_arq finds the first (lowest sector numbered) request
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* for the specified data_dir. Used to sweep back to the start of the disk
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* (1-way elevator) after we process the last (highest sector) request.
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*/
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static struct as_rq *as_find_first_arq(struct as_data *ad, int data_dir)
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{
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struct rb_node *n = ad->sort_list[data_dir].rb_node;
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if (n == NULL)
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return NULL;
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for (;;) {
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if (n->rb_left == NULL)
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return rb_entry_arq(n);
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n = n->rb_left;
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}
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}
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/*
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* Add the request to the rb tree if it is unique. If there is an alias (an
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* existing request against the same sector), which can happen when using
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* direct IO, then return the alias.
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*/
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static struct as_rq *__as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
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{
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struct rb_node **p = &ARQ_RB_ROOT(ad, arq)->rb_node;
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struct rb_node *parent = NULL;
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struct as_rq *__arq;
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struct request *rq = arq->request;
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arq->rb_key = rq_rb_key(rq);
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while (*p) {
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parent = *p;
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__arq = rb_entry_arq(parent);
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if (arq->rb_key < __arq->rb_key)
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p = &(*p)->rb_left;
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else if (arq->rb_key > __arq->rb_key)
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p = &(*p)->rb_right;
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else
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return __arq;
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}
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rb_link_node(&arq->rb_node, parent, p);
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rb_insert_color(&arq->rb_node, ARQ_RB_ROOT(ad, arq));
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return NULL;
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}
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static void as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
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{
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struct as_rq *alias;
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while ((unlikely(alias = __as_add_arq_rb(ad, arq)))) {
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as_move_to_dispatch(ad, alias);
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as_antic_stop(ad);
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}
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}
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static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq)
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{
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if (!ON_RB(&arq->rb_node)) {
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WARN_ON(1);
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return;
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}
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rb_erase(&arq->rb_node, ARQ_RB_ROOT(ad, arq));
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RB_CLEAR(&arq->rb_node);
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}
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static struct request *
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as_find_arq_rb(struct as_data *ad, sector_t sector, int data_dir)
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{
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struct rb_node *n = ad->sort_list[data_dir].rb_node;
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struct as_rq *arq;
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while (n) {
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arq = rb_entry_arq(n);
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if (sector < arq->rb_key)
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n = n->rb_left;
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else if (sector > arq->rb_key)
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n = n->rb_right;
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else
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return arq->request;
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}
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return NULL;
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}
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/*
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* IO Scheduler proper
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*/
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#define MAXBACK (1024 * 1024) /*
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* Maximum distance the disk will go backward
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* for a request.
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*/
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#define BACK_PENALTY 2
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/*
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* as_choose_req selects the preferred one of two requests of the same data_dir
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* ignoring time - eg. timeouts, which is the job of as_dispatch_request
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*/
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static struct as_rq *
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as_choose_req(struct as_data *ad, struct as_rq *arq1, struct as_rq *arq2)
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{
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int data_dir;
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sector_t last, s1, s2, d1, d2;
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int r1_wrap=0, r2_wrap=0; /* requests are behind the disk head */
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const sector_t maxback = MAXBACK;
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if (arq1 == NULL || arq1 == arq2)
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return arq2;
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if (arq2 == NULL)
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return arq1;
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data_dir = arq1->is_sync;
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last = ad->last_sector[data_dir];
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s1 = arq1->request->sector;
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s2 = arq2->request->sector;
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BUG_ON(data_dir != arq2->is_sync);
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/*
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* Strict one way elevator _except_ in the case where we allow
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* short backward seeks which are biased as twice the cost of a
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* similar forward seek.
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*/
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if (s1 >= last)
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d1 = s1 - last;
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else if (s1+maxback >= last)
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d1 = (last - s1)*BACK_PENALTY;
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else {
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r1_wrap = 1;
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d1 = 0; /* shut up, gcc */
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}
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if (s2 >= last)
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d2 = s2 - last;
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else if (s2+maxback >= last)
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d2 = (last - s2)*BACK_PENALTY;
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else {
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r2_wrap = 1;
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d2 = 0;
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}
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/* Found required data */
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if (!r1_wrap && r2_wrap)
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return arq1;
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else if (!r2_wrap && r1_wrap)
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return arq2;
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else if (r1_wrap && r2_wrap) {
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/* both behind the head */
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if (s1 <= s2)
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return arq1;
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else
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return arq2;
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}
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|
|
/* Both requests in front of the head */
|
|
if (d1 < d2)
|
|
return arq1;
|
|
else if (d2 < d1)
|
|
return arq2;
|
|
else {
|
|
if (s1 >= s2)
|
|
return arq1;
|
|
else
|
|
return arq2;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* as_find_next_arq finds the next request after @prev in elevator order.
|
|
* this with as_choose_req form the basis for how the scheduler chooses
|
|
* what request to process next. Anticipation works on top of this.
|
|
*/
|
|
static struct as_rq *as_find_next_arq(struct as_data *ad, struct as_rq *last)
|
|
{
|
|
const int data_dir = last->is_sync;
|
|
struct as_rq *ret;
|
|
struct rb_node *rbnext = rb_next(&last->rb_node);
|
|
struct rb_node *rbprev = rb_prev(&last->rb_node);
|
|
struct as_rq *arq_next, *arq_prev;
|
|
|
|
BUG_ON(!ON_RB(&last->rb_node));
|
|
|
|
if (rbprev)
|
|
arq_prev = rb_entry_arq(rbprev);
|
|
else
|
|
arq_prev = NULL;
|
|
|
|
if (rbnext)
|
|
arq_next = rb_entry_arq(rbnext);
|
|
else {
|
|
arq_next = as_find_first_arq(ad, data_dir);
|
|
if (arq_next == last)
|
|
arq_next = NULL;
|
|
}
|
|
|
|
ret = as_choose_req(ad, arq_next, arq_prev);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* anticipatory scheduling functions follow
|
|
*/
|
|
|
|
/*
|
|
* as_antic_expired tells us when we have anticipated too long.
|
|
* The funny "absolute difference" math on the elapsed time is to handle
|
|
* jiffy wraps, and disks which have been idle for 0x80000000 jiffies.
|
|
*/
|
|
static int as_antic_expired(struct as_data *ad)
|
|
{
|
|
long delta_jif;
|
|
|
|
delta_jif = jiffies - ad->antic_start;
|
|
if (unlikely(delta_jif < 0))
|
|
delta_jif = -delta_jif;
|
|
if (delta_jif < ad->antic_expire)
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* as_antic_waitnext starts anticipating that a nice request will soon be
|
|
* submitted. See also as_antic_waitreq
|
|
*/
|
|
static void as_antic_waitnext(struct as_data *ad)
|
|
{
|
|
unsigned long timeout;
|
|
|
|
BUG_ON(ad->antic_status != ANTIC_OFF
|
|
&& ad->antic_status != ANTIC_WAIT_REQ);
|
|
|
|
timeout = ad->antic_start + ad->antic_expire;
|
|
|
|
mod_timer(&ad->antic_timer, timeout);
|
|
|
|
ad->antic_status = ANTIC_WAIT_NEXT;
|
|
}
|
|
|
|
/*
|
|
* as_antic_waitreq starts anticipating. We don't start timing the anticipation
|
|
* until the request that we're anticipating on has finished. This means we
|
|
* are timing from when the candidate process wakes up hopefully.
|
|
*/
|
|
static void as_antic_waitreq(struct as_data *ad)
|
|
{
|
|
BUG_ON(ad->antic_status == ANTIC_FINISHED);
|
|
if (ad->antic_status == ANTIC_OFF) {
|
|
if (!ad->io_context || ad->ioc_finished)
|
|
as_antic_waitnext(ad);
|
|
else
|
|
ad->antic_status = ANTIC_WAIT_REQ;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This is called directly by the functions in this file to stop anticipation.
|
|
* We kill the timer and schedule a call to the request_fn asap.
|
|
*/
|
|
static void as_antic_stop(struct as_data *ad)
|
|
{
|
|
int status = ad->antic_status;
|
|
|
|
if (status == ANTIC_WAIT_REQ || status == ANTIC_WAIT_NEXT) {
|
|
if (status == ANTIC_WAIT_NEXT)
|
|
del_timer(&ad->antic_timer);
|
|
ad->antic_status = ANTIC_FINISHED;
|
|
/* see as_work_handler */
|
|
kblockd_schedule_work(&ad->antic_work);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* as_antic_timeout is the timer function set by as_antic_waitnext.
|
|
*/
|
|
static void as_antic_timeout(unsigned long data)
|
|
{
|
|
struct request_queue *q = (struct request_queue *)data;
|
|
struct as_data *ad = q->elevator->elevator_data;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(q->queue_lock, flags);
|
|
if (ad->antic_status == ANTIC_WAIT_REQ
|
|
|| ad->antic_status == ANTIC_WAIT_NEXT) {
|
|
struct as_io_context *aic = ad->io_context->aic;
|
|
|
|
ad->antic_status = ANTIC_FINISHED;
|
|
kblockd_schedule_work(&ad->antic_work);
|
|
|
|
if (aic->ttime_samples == 0) {
|
|
/* process anticipated on has exited or timed out*/
|
|
ad->exit_prob = (7*ad->exit_prob + 256)/8;
|
|
}
|
|
if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
|
|
/* process not "saved" by a cooperating request */
|
|
ad->exit_no_coop = (7*ad->exit_no_coop + 256)/8;
|
|
}
|
|
}
|
|
spin_unlock_irqrestore(q->queue_lock, flags);
|
|
}
|
|
|
|
static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic,
|
|
unsigned long ttime)
|
|
{
|
|
/* fixed point: 1.0 == 1<<8 */
|
|
if (aic->ttime_samples == 0) {
|
|
ad->new_ttime_total = (7*ad->new_ttime_total + 256*ttime) / 8;
|
|
ad->new_ttime_mean = ad->new_ttime_total / 256;
|
|
|
|
ad->exit_prob = (7*ad->exit_prob)/8;
|
|
}
|
|
aic->ttime_samples = (7*aic->ttime_samples + 256) / 8;
|
|
aic->ttime_total = (7*aic->ttime_total + 256*ttime) / 8;
|
|
aic->ttime_mean = (aic->ttime_total + 128) / aic->ttime_samples;
|
|
}
|
|
|
|
static void as_update_seekdist(struct as_data *ad, struct as_io_context *aic,
|
|
sector_t sdist)
|
|
{
|
|
u64 total;
|
|
|
|
if (aic->seek_samples == 0) {
|
|
ad->new_seek_total = (7*ad->new_seek_total + 256*(u64)sdist)/8;
|
|
ad->new_seek_mean = ad->new_seek_total / 256;
|
|
}
|
|
|
|
/*
|
|
* Don't allow the seek distance to get too large from the
|
|
* odd fragment, pagein, etc
|
|
*/
|
|
if (aic->seek_samples <= 60) /* second&third seek */
|
|
sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*1024);
|
|
else
|
|
sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*64);
|
|
|
|
aic->seek_samples = (7*aic->seek_samples + 256) / 8;
|
|
aic->seek_total = (7*aic->seek_total + (u64)256*sdist) / 8;
|
|
total = aic->seek_total + (aic->seek_samples/2);
|
|
do_div(total, aic->seek_samples);
|
|
aic->seek_mean = (sector_t)total;
|
|
}
|
|
|
|
/*
|
|
* as_update_iohist keeps a decaying histogram of IO thinktimes, and
|
|
* updates @aic->ttime_mean based on that. It is called when a new
|
|
* request is queued.
|
|
*/
|
|
static void as_update_iohist(struct as_data *ad, struct as_io_context *aic,
|
|
struct request *rq)
|
|
{
|
|
struct as_rq *arq = RQ_DATA(rq);
|
|
int data_dir = arq->is_sync;
|
|
unsigned long thinktime = 0;
|
|
sector_t seek_dist;
|
|
|
|
if (aic == NULL)
|
|
return;
|
|
|
|
if (data_dir == REQ_SYNC) {
|
|
unsigned long in_flight = atomic_read(&aic->nr_queued)
|
|
+ atomic_read(&aic->nr_dispatched);
|
|
spin_lock(&aic->lock);
|
|
if (test_bit(AS_TASK_IORUNNING, &aic->state) ||
|
|
test_bit(AS_TASK_IOSTARTED, &aic->state)) {
|
|
/* Calculate read -> read thinktime */
|
|
if (test_bit(AS_TASK_IORUNNING, &aic->state)
|
|
&& in_flight == 0) {
|
|
thinktime = jiffies - aic->last_end_request;
|
|
thinktime = min(thinktime, MAX_THINKTIME-1);
|
|
}
|
|
as_update_thinktime(ad, aic, thinktime);
|
|
|
|
/* Calculate read -> read seek distance */
|
|
if (aic->last_request_pos < rq->sector)
|
|
seek_dist = rq->sector - aic->last_request_pos;
|
|
else
|
|
seek_dist = aic->last_request_pos - rq->sector;
|
|
as_update_seekdist(ad, aic, seek_dist);
|
|
}
|
|
aic->last_request_pos = rq->sector + rq->nr_sectors;
|
|
set_bit(AS_TASK_IOSTARTED, &aic->state);
|
|
spin_unlock(&aic->lock);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* as_close_req decides if one request is considered "close" to the
|
|
* previous one issued.
|
|
*/
|
|
static int as_close_req(struct as_data *ad, struct as_io_context *aic,
|
|
struct as_rq *arq)
|
|
{
|
|
unsigned long delay; /* milliseconds */
|
|
sector_t last = ad->last_sector[ad->batch_data_dir];
|
|
sector_t next = arq->request->sector;
|
|
sector_t delta; /* acceptable close offset (in sectors) */
|
|
sector_t s;
|
|
|
|
if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished)
|
|
delay = 0;
|
|
else
|
|
delay = ((jiffies - ad->antic_start) * 1000) / HZ;
|
|
|
|
if (delay == 0)
|
|
delta = 8192;
|
|
else if (delay <= 20 && delay <= ad->antic_expire)
|
|
delta = 8192 << delay;
|
|
else
|
|
return 1;
|
|
|
|
if ((last <= next + (delta>>1)) && (next <= last + delta))
|
|
return 1;
|
|
|
|
if (last < next)
|
|
s = next - last;
|
|
else
|
|
s = last - next;
|
|
|
|
if (aic->seek_samples == 0) {
|
|
/*
|
|
* Process has just started IO. Use past statistics to
|
|
* gauge success possibility
|
|
*/
|
|
if (ad->new_seek_mean > s) {
|
|
/* this request is better than what we're expecting */
|
|
return 1;
|
|
}
|
|
|
|
} else {
|
|
if (aic->seek_mean > s) {
|
|
/* this request is better than what we're expecting */
|
|
return 1;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* as_can_break_anticipation returns true if we have been anticipating this
|
|
* request.
|
|
*
|
|
* It also returns true if the process against which we are anticipating
|
|
* submits a write - that's presumably an fsync, O_SYNC write, etc. We want to
|
|
* dispatch it ASAP, because we know that application will not be submitting
|
|
* any new reads.
|
|
*
|
|
* If the task which has submitted the request has exited, break anticipation.
|
|
*
|
|
* If this task has queued some other IO, do not enter enticipation.
|
|
*/
|
|
static int as_can_break_anticipation(struct as_data *ad, struct as_rq *arq)
|
|
{
|
|
struct io_context *ioc;
|
|
struct as_io_context *aic;
|
|
|
|
ioc = ad->io_context;
|
|
BUG_ON(!ioc);
|
|
|
|
if (arq && ioc == arq->io_context) {
|
|
/* request from same process */
|
|
return 1;
|
|
}
|
|
|
|
if (ad->ioc_finished && as_antic_expired(ad)) {
|
|
/*
|
|
* In this situation status should really be FINISHED,
|
|
* however the timer hasn't had the chance to run yet.
|
|
*/
|
|
return 1;
|
|
}
|
|
|
|
aic = ioc->aic;
|
|
if (!aic)
|
|
return 0;
|
|
|
|
if (atomic_read(&aic->nr_queued) > 0) {
|
|
/* process has more requests queued */
|
|
return 1;
|
|
}
|
|
|
|
if (atomic_read(&aic->nr_dispatched) > 0) {
|
|
/* process has more requests dispatched */
|
|
return 1;
|
|
}
|
|
|
|
if (arq && arq->is_sync == REQ_SYNC && as_close_req(ad, aic, arq)) {
|
|
/*
|
|
* Found a close request that is not one of ours.
|
|
*
|
|
* This makes close requests from another process update
|
|
* our IO history. Is generally useful when there are
|
|
* two or more cooperating processes working in the same
|
|
* area.
|
|
*/
|
|
if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
|
|
if (aic->ttime_samples == 0)
|
|
ad->exit_prob = (7*ad->exit_prob + 256)/8;
|
|
|
|
ad->exit_no_coop = (7*ad->exit_no_coop)/8;
|
|
}
|
|
|
|
as_update_iohist(ad, aic, arq->request);
|
|
return 1;
|
|
}
|
|
|
|
if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
|
|
/* process anticipated on has exited */
|
|
if (aic->ttime_samples == 0)
|
|
ad->exit_prob = (7*ad->exit_prob + 256)/8;
|
|
|
|
if (ad->exit_no_coop > 128)
|
|
return 1;
|
|
}
|
|
|
|
if (aic->ttime_samples == 0) {
|
|
if (ad->new_ttime_mean > ad->antic_expire)
|
|
return 1;
|
|
if (ad->exit_prob * ad->exit_no_coop > 128*256)
|
|
return 1;
|
|
} else if (aic->ttime_mean > ad->antic_expire) {
|
|
/* the process thinks too much between requests */
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* as_can_anticipate indicates weather we should either run arq
|
|
* or keep anticipating a better request.
|
|
*/
|
|
static int as_can_anticipate(struct as_data *ad, struct as_rq *arq)
|
|
{
|
|
if (!ad->io_context)
|
|
/*
|
|
* Last request submitted was a write
|
|
*/
|
|
return 0;
|
|
|
|
if (ad->antic_status == ANTIC_FINISHED)
|
|
/*
|
|
* Don't restart if we have just finished. Run the next request
|
|
*/
|
|
return 0;
|
|
|
|
if (as_can_break_anticipation(ad, arq))
|
|
/*
|
|
* This request is a good candidate. Don't keep anticipating,
|
|
* run it.
|
|
*/
|
|
return 0;
|
|
|
|
/*
|
|
* OK from here, we haven't finished, and don't have a decent request!
|
|
* Status is either ANTIC_OFF so start waiting,
|
|
* ANTIC_WAIT_REQ so continue waiting for request to finish
|
|
* or ANTIC_WAIT_NEXT so continue waiting for an acceptable request.
|
|
*/
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* as_update_arq must be called whenever a request (arq) is added to
|
|
* the sort_list. This function keeps caches up to date, and checks if the
|
|
* request might be one we are "anticipating"
|
|
*/
|
|
static void as_update_arq(struct as_data *ad, struct as_rq *arq)
|
|
{
|
|
const int data_dir = arq->is_sync;
|
|
|
|
/* keep the next_arq cache up to date */
|
|
ad->next_arq[data_dir] = as_choose_req(ad, arq, ad->next_arq[data_dir]);
|
|
|
|
/*
|
|
* have we been anticipating this request?
|
|
* or does it come from the same process as the one we are anticipating
|
|
* for?
|
|
*/
|
|
if (ad->antic_status == ANTIC_WAIT_REQ
|
|
|| ad->antic_status == ANTIC_WAIT_NEXT) {
|
|
if (as_can_break_anticipation(ad, arq))
|
|
as_antic_stop(ad);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Gathers timings and resizes the write batch automatically
|
|
*/
|
|
static void update_write_batch(struct as_data *ad)
|
|
{
|
|
unsigned long batch = ad->batch_expire[REQ_ASYNC];
|
|
long write_time;
|
|
|
|
write_time = (jiffies - ad->current_batch_expires) + batch;
|
|
if (write_time < 0)
|
|
write_time = 0;
|
|
|
|
if (write_time > batch && !ad->write_batch_idled) {
|
|
if (write_time > batch * 3)
|
|
ad->write_batch_count /= 2;
|
|
else
|
|
ad->write_batch_count--;
|
|
} else if (write_time < batch && ad->current_write_count == 0) {
|
|
if (batch > write_time * 3)
|
|
ad->write_batch_count *= 2;
|
|
else
|
|
ad->write_batch_count++;
|
|
}
|
|
|
|
if (ad->write_batch_count < 1)
|
|
ad->write_batch_count = 1;
|
|
}
|
|
|
|
/*
|
|
* as_completed_request is to be called when a request has completed and
|
|
* returned something to the requesting process, be it an error or data.
|
|
*/
|
|
static void as_completed_request(request_queue_t *q, struct request *rq)
|
|
{
|
|
struct as_data *ad = q->elevator->elevator_data;
|
|
struct as_rq *arq = RQ_DATA(rq);
|
|
|
|
WARN_ON(!list_empty(&rq->queuelist));
|
|
|
|
if (arq->state != AS_RQ_REMOVED) {
|
|
printk("arq->state %d\n", arq->state);
|
|
WARN_ON(1);
|
|
goto out;
|
|
}
|
|
|
|
if (ad->changed_batch && ad->nr_dispatched == 1) {
|
|
kblockd_schedule_work(&ad->antic_work);
|
|
ad->changed_batch = 0;
|
|
|
|
if (ad->batch_data_dir == REQ_SYNC)
|
|
ad->new_batch = 1;
|
|
}
|
|
WARN_ON(ad->nr_dispatched == 0);
|
|
ad->nr_dispatched--;
|
|
|
|
/*
|
|
* Start counting the batch from when a request of that direction is
|
|
* actually serviced. This should help devices with big TCQ windows
|
|
* and writeback caches
|
|
*/
|
|
if (ad->new_batch && ad->batch_data_dir == arq->is_sync) {
|
|
update_write_batch(ad);
|
|
ad->current_batch_expires = jiffies +
|
|
ad->batch_expire[REQ_SYNC];
|
|
ad->new_batch = 0;
|
|
}
|
|
|
|
if (ad->io_context == arq->io_context && ad->io_context) {
|
|
ad->antic_start = jiffies;
|
|
ad->ioc_finished = 1;
|
|
if (ad->antic_status == ANTIC_WAIT_REQ) {
|
|
/*
|
|
* We were waiting on this request, now anticipate
|
|
* the next one
|
|
*/
|
|
as_antic_waitnext(ad);
|
|
}
|
|
}
|
|
|
|
as_put_io_context(arq);
|
|
out:
|
|
arq->state = AS_RQ_POSTSCHED;
|
|
}
|
|
|
|
/*
|
|
* as_remove_queued_request removes a request from the pre dispatch queue
|
|
* without updating refcounts. It is expected the caller will drop the
|
|
* reference unless it replaces the request at somepart of the elevator
|
|
* (ie. the dispatch queue)
|
|
*/
|
|
static void as_remove_queued_request(request_queue_t *q, struct request *rq)
|
|
{
|
|
struct as_rq *arq = RQ_DATA(rq);
|
|
const int data_dir = arq->is_sync;
|
|
struct as_data *ad = q->elevator->elevator_data;
|
|
|
|
WARN_ON(arq->state != AS_RQ_QUEUED);
|
|
|
|
if (arq->io_context && arq->io_context->aic) {
|
|
BUG_ON(!atomic_read(&arq->io_context->aic->nr_queued));
|
|
atomic_dec(&arq->io_context->aic->nr_queued);
|
|
}
|
|
|
|
/*
|
|
* Update the "next_arq" cache if we are about to remove its
|
|
* entry
|
|
*/
|
|
if (ad->next_arq[data_dir] == arq)
|
|
ad->next_arq[data_dir] = as_find_next_arq(ad, arq);
|
|
|
|
list_del_init(&arq->fifo);
|
|
as_del_arq_hash(arq);
|
|
as_del_arq_rb(ad, arq);
|
|
}
|
|
|
|
/*
|
|
* as_fifo_expired returns 0 if there are no expired reads on the fifo,
|
|
* 1 otherwise. It is ratelimited so that we only perform the check once per
|
|
* `fifo_expire' interval. Otherwise a large number of expired requests
|
|
* would create a hopeless seekstorm.
|
|
*
|
|
* See as_antic_expired comment.
|
|
*/
|
|
static int as_fifo_expired(struct as_data *ad, int adir)
|
|
{
|
|
struct as_rq *arq;
|
|
long delta_jif;
|
|
|
|
delta_jif = jiffies - ad->last_check_fifo[adir];
|
|
if (unlikely(delta_jif < 0))
|
|
delta_jif = -delta_jif;
|
|
if (delta_jif < ad->fifo_expire[adir])
|
|
return 0;
|
|
|
|
ad->last_check_fifo[adir] = jiffies;
|
|
|
|
if (list_empty(&ad->fifo_list[adir]))
|
|
return 0;
|
|
|
|
arq = list_entry_fifo(ad->fifo_list[adir].next);
|
|
|
|
return time_after(jiffies, arq->expires);
|
|
}
|
|
|
|
/*
|
|
* as_batch_expired returns true if the current batch has expired. A batch
|
|
* is a set of reads or a set of writes.
|
|
*/
|
|
static inline int as_batch_expired(struct as_data *ad)
|
|
{
|
|
if (ad->changed_batch || ad->new_batch)
|
|
return 0;
|
|
|
|
if (ad->batch_data_dir == REQ_SYNC)
|
|
/* TODO! add a check so a complete fifo gets written? */
|
|
return time_after(jiffies, ad->current_batch_expires);
|
|
|
|
return time_after(jiffies, ad->current_batch_expires)
|
|
|| ad->current_write_count == 0;
|
|
}
|
|
|
|
/*
|
|
* move an entry to dispatch queue
|
|
*/
|
|
static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
|
|
{
|
|
struct request *rq = arq->request;
|
|
const int data_dir = arq->is_sync;
|
|
|
|
BUG_ON(!ON_RB(&arq->rb_node));
|
|
|
|
as_antic_stop(ad);
|
|
ad->antic_status = ANTIC_OFF;
|
|
|
|
/*
|
|
* This has to be set in order to be correctly updated by
|
|
* as_find_next_arq
|
|
*/
|
|
ad->last_sector[data_dir] = rq->sector + rq->nr_sectors;
|
|
|
|
if (data_dir == REQ_SYNC) {
|
|
/* In case we have to anticipate after this */
|
|
copy_io_context(&ad->io_context, &arq->io_context);
|
|
} else {
|
|
if (ad->io_context) {
|
|
put_io_context(ad->io_context);
|
|
ad->io_context = NULL;
|
|
}
|
|
|
|
if (ad->current_write_count != 0)
|
|
ad->current_write_count--;
|
|
}
|
|
ad->ioc_finished = 0;
|
|
|
|
ad->next_arq[data_dir] = as_find_next_arq(ad, arq);
|
|
|
|
/*
|
|
* take it off the sort and fifo list, add to dispatch queue
|
|
*/
|
|
as_remove_queued_request(ad->q, rq);
|
|
WARN_ON(arq->state != AS_RQ_QUEUED);
|
|
|
|
elv_dispatch_sort(ad->q, rq);
|
|
|
|
arq->state = AS_RQ_DISPATCHED;
|
|
if (arq->io_context && arq->io_context->aic)
|
|
atomic_inc(&arq->io_context->aic->nr_dispatched);
|
|
ad->nr_dispatched++;
|
|
}
|
|
|
|
/*
|
|
* as_dispatch_request selects the best request according to
|
|
* read/write expire, batch expire, etc, and moves it to the dispatch
|
|
* queue. Returns 1 if a request was found, 0 otherwise.
|
|
*/
|
|
static int as_dispatch_request(request_queue_t *q, int force)
|
|
{
|
|
struct as_data *ad = q->elevator->elevator_data;
|
|
struct as_rq *arq;
|
|
const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]);
|
|
const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]);
|
|
|
|
if (unlikely(force)) {
|
|
/*
|
|
* Forced dispatch, accounting is useless. Reset
|
|
* accounting states and dump fifo_lists. Note that
|
|
* batch_data_dir is reset to REQ_SYNC to avoid
|
|
* screwing write batch accounting as write batch
|
|
* accounting occurs on W->R transition.
|
|
*/
|
|
int dispatched = 0;
|
|
|
|
ad->batch_data_dir = REQ_SYNC;
|
|
ad->changed_batch = 0;
|
|
ad->new_batch = 0;
|
|
|
|
while (ad->next_arq[REQ_SYNC]) {
|
|
as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]);
|
|
dispatched++;
|
|
}
|
|
ad->last_check_fifo[REQ_SYNC] = jiffies;
|
|
|
|
while (ad->next_arq[REQ_ASYNC]) {
|
|
as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]);
|
|
dispatched++;
|
|
}
|
|
ad->last_check_fifo[REQ_ASYNC] = jiffies;
|
|
|
|
return dispatched;
|
|
}
|
|
|
|
/* Signal that the write batch was uncontended, so we can't time it */
|
|
if (ad->batch_data_dir == REQ_ASYNC && !reads) {
|
|
if (ad->current_write_count == 0 || !writes)
|
|
ad->write_batch_idled = 1;
|
|
}
|
|
|
|
if (!(reads || writes)
|
|
|| ad->antic_status == ANTIC_WAIT_REQ
|
|
|| ad->antic_status == ANTIC_WAIT_NEXT
|
|
|| ad->changed_batch)
|
|
return 0;
|
|
|
|
if (!(reads && writes && as_batch_expired(ad))) {
|
|
/*
|
|
* batch is still running or no reads or no writes
|
|
*/
|
|
arq = ad->next_arq[ad->batch_data_dir];
|
|
|
|
if (ad->batch_data_dir == REQ_SYNC && ad->antic_expire) {
|
|
if (as_fifo_expired(ad, REQ_SYNC))
|
|
goto fifo_expired;
|
|
|
|
if (as_can_anticipate(ad, arq)) {
|
|
as_antic_waitreq(ad);
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
if (arq) {
|
|
/* we have a "next request" */
|
|
if (reads && !writes)
|
|
ad->current_batch_expires =
|
|
jiffies + ad->batch_expire[REQ_SYNC];
|
|
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(&ad->sort_list[REQ_SYNC]));
|
|
|
|
if (writes && ad->batch_data_dir == REQ_SYNC)
|
|
/*
|
|
* Last batch was a read, switch to writes
|
|
*/
|
|
goto dispatch_writes;
|
|
|
|
if (ad->batch_data_dir == REQ_ASYNC) {
|
|
WARN_ON(ad->new_batch);
|
|
ad->changed_batch = 1;
|
|
}
|
|
ad->batch_data_dir = REQ_SYNC;
|
|
arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
|
|
ad->last_check_fifo[ad->batch_data_dir] = jiffies;
|
|
goto dispatch_request;
|
|
}
|
|
|
|
/*
|
|
* the last batch was a read
|
|
*/
|
|
|
|
if (writes) {
|
|
dispatch_writes:
|
|
BUG_ON(RB_EMPTY(&ad->sort_list[REQ_ASYNC]));
|
|
|
|
if (ad->batch_data_dir == REQ_SYNC) {
|
|
ad->changed_batch = 1;
|
|
|
|
/*
|
|
* new_batch might be 1 when the queue runs out of
|
|
* reads. A subsequent submission of a write might
|
|
* cause a change of batch before the read is finished.
|
|
*/
|
|
ad->new_batch = 0;
|
|
}
|
|
ad->batch_data_dir = REQ_ASYNC;
|
|
ad->current_write_count = ad->write_batch_count;
|
|
ad->write_batch_idled = 0;
|
|
arq = ad->next_arq[ad->batch_data_dir];
|
|
goto dispatch_request;
|
|
}
|
|
|
|
BUG();
|
|
return 0;
|
|
|
|
dispatch_request:
|
|
/*
|
|
* If a request has expired, service it.
|
|
*/
|
|
|
|
if (as_fifo_expired(ad, ad->batch_data_dir)) {
|
|
fifo_expired:
|
|
arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
|
|
BUG_ON(arq == NULL);
|
|
}
|
|
|
|
if (ad->changed_batch) {
|
|
WARN_ON(ad->new_batch);
|
|
|
|
if (ad->nr_dispatched)
|
|
return 0;
|
|
|
|
if (ad->batch_data_dir == REQ_ASYNC)
|
|
ad->current_batch_expires = jiffies +
|
|
ad->batch_expire[REQ_ASYNC];
|
|
else
|
|
ad->new_batch = 1;
|
|
|
|
ad->changed_batch = 0;
|
|
}
|
|
|
|
/*
|
|
* arq is the selected appropriate request.
|
|
*/
|
|
as_move_to_dispatch(ad, arq);
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* add arq to rbtree and fifo
|
|
*/
|
|
static void as_add_request(request_queue_t *q, struct request *rq)
|
|
{
|
|
struct as_data *ad = q->elevator->elevator_data;
|
|
struct as_rq *arq = RQ_DATA(rq);
|
|
int data_dir;
|
|
|
|
arq->state = AS_RQ_NEW;
|
|
|
|
if (rq_data_dir(arq->request) == READ
|
|
|| current->flags&PF_SYNCWRITE)
|
|
arq->is_sync = 1;
|
|
else
|
|
arq->is_sync = 0;
|
|
data_dir = arq->is_sync;
|
|
|
|
arq->io_context = as_get_io_context();
|
|
|
|
if (arq->io_context) {
|
|
as_update_iohist(ad, arq->io_context->aic, arq->request);
|
|
atomic_inc(&arq->io_context->aic->nr_queued);
|
|
}
|
|
|
|
as_add_arq_rb(ad, arq);
|
|
if (rq_mergeable(arq->request))
|
|
as_add_arq_hash(ad, arq);
|
|
|
|
/*
|
|
* set expire time (only used for reads) and add to fifo list
|
|
*/
|
|
arq->expires = jiffies + ad->fifo_expire[data_dir];
|
|
list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]);
|
|
|
|
as_update_arq(ad, arq); /* keep state machine up to date */
|
|
arq->state = AS_RQ_QUEUED;
|
|
}
|
|
|
|
static void as_activate_request(request_queue_t *q, struct request *rq)
|
|
{
|
|
struct as_rq *arq = RQ_DATA(rq);
|
|
|
|
WARN_ON(arq->state != AS_RQ_DISPATCHED);
|
|
arq->state = AS_RQ_REMOVED;
|
|
if (arq->io_context && arq->io_context->aic)
|
|
atomic_dec(&arq->io_context->aic->nr_dispatched);
|
|
}
|
|
|
|
static void as_deactivate_request(request_queue_t *q, struct request *rq)
|
|
{
|
|
struct as_rq *arq = RQ_DATA(rq);
|
|
|
|
WARN_ON(arq->state != AS_RQ_REMOVED);
|
|
arq->state = AS_RQ_DISPATCHED;
|
|
if (arq->io_context && arq->io_context->aic)
|
|
atomic_inc(&arq->io_context->aic->nr_dispatched);
|
|
}
|
|
|
|
/*
|
|
* as_queue_empty tells us if there are requests left in the device. It may
|
|
* not be the case that a driver can get the next request even if the queue
|
|
* is not empty - it is used in the block layer to check for plugging and
|
|
* merging opportunities
|
|
*/
|
|
static int as_queue_empty(request_queue_t *q)
|
|
{
|
|
struct as_data *ad = q->elevator->elevator_data;
|
|
|
|
return list_empty(&ad->fifo_list[REQ_ASYNC])
|
|
&& list_empty(&ad->fifo_list[REQ_SYNC]);
|
|
}
|
|
|
|
static struct request *as_former_request(request_queue_t *q,
|
|
struct request *rq)
|
|
{
|
|
struct as_rq *arq = RQ_DATA(rq);
|
|
struct rb_node *rbprev = rb_prev(&arq->rb_node);
|
|
struct request *ret = NULL;
|
|
|
|
if (rbprev)
|
|
ret = rb_entry_arq(rbprev)->request;
|
|
|
|
return ret;
|
|
}
|
|
|
|
static struct request *as_latter_request(request_queue_t *q,
|
|
struct request *rq)
|
|
{
|
|
struct as_rq *arq = RQ_DATA(rq);
|
|
struct rb_node *rbnext = rb_next(&arq->rb_node);
|
|
struct request *ret = NULL;
|
|
|
|
if (rbnext)
|
|
ret = rb_entry_arq(rbnext)->request;
|
|
|
|
return ret;
|
|
}
|
|
|
|
static int
|
|
as_merge(request_queue_t *q, struct request **req, struct bio *bio)
|
|
{
|
|
struct as_data *ad = q->elevator->elevator_data;
|
|
sector_t rb_key = bio->bi_sector + bio_sectors(bio);
|
|
struct request *__rq;
|
|
int ret;
|
|
|
|
/*
|
|
* see if the merge hash can satisfy a back merge
|
|
*/
|
|
__rq = as_find_arq_hash(ad, bio->bi_sector);
|
|
if (__rq) {
|
|
BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector);
|
|
|
|
if (elv_rq_merge_ok(__rq, bio)) {
|
|
ret = ELEVATOR_BACK_MERGE;
|
|
goto out;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* check for front merge
|
|
*/
|
|
__rq = as_find_arq_rb(ad, rb_key, bio_data_dir(bio));
|
|
if (__rq) {
|
|
BUG_ON(rb_key != rq_rb_key(__rq));
|
|
|
|
if (elv_rq_merge_ok(__rq, bio)) {
|
|
ret = ELEVATOR_FRONT_MERGE;
|
|
goto out;
|
|
}
|
|
}
|
|
|
|
return ELEVATOR_NO_MERGE;
|
|
out:
|
|
if (ret) {
|
|
if (rq_mergeable(__rq))
|
|
as_hot_arq_hash(ad, RQ_DATA(__rq));
|
|
}
|
|
*req = __rq;
|
|
return ret;
|
|
}
|
|
|
|
static void as_merged_request(request_queue_t *q, struct request *req)
|
|
{
|
|
struct as_data *ad = q->elevator->elevator_data;
|
|
struct as_rq *arq = RQ_DATA(req);
|
|
|
|
/*
|
|
* hash always needs to be repositioned, key is end sector
|
|
*/
|
|
as_del_arq_hash(arq);
|
|
as_add_arq_hash(ad, arq);
|
|
|
|
/*
|
|
* if the merge was a front merge, we need to reposition request
|
|
*/
|
|
if (rq_rb_key(req) != arq->rb_key) {
|
|
as_del_arq_rb(ad, arq);
|
|
as_add_arq_rb(ad, arq);
|
|
/*
|
|
* Note! At this stage of this and the next function, our next
|
|
* request may not be optimal - eg the request may have "grown"
|
|
* behind the disk head. We currently don't bother adjusting.
|
|
*/
|
|
}
|
|
}
|
|
|
|
static void as_merged_requests(request_queue_t *q, struct request *req,
|
|
struct request *next)
|
|
{
|
|
struct as_data *ad = q->elevator->elevator_data;
|
|
struct as_rq *arq = RQ_DATA(req);
|
|
struct as_rq *anext = RQ_DATA(next);
|
|
|
|
BUG_ON(!arq);
|
|
BUG_ON(!anext);
|
|
|
|
/*
|
|
* reposition arq (this is the merged request) in hash, and in rbtree
|
|
* in case of a front merge
|
|
*/
|
|
as_del_arq_hash(arq);
|
|
as_add_arq_hash(ad, arq);
|
|
|
|
if (rq_rb_key(req) != arq->rb_key) {
|
|
as_del_arq_rb(ad, arq);
|
|
as_add_arq_rb(ad, arq);
|
|
}
|
|
|
|
/*
|
|
* if anext expires before arq, assign its expire time to arq
|
|
* and move into anext position (anext will be deleted) in fifo
|
|
*/
|
|
if (!list_empty(&arq->fifo) && !list_empty(&anext->fifo)) {
|
|
if (time_before(anext->expires, arq->expires)) {
|
|
list_move(&arq->fifo, &anext->fifo);
|
|
arq->expires = anext->expires;
|
|
/*
|
|
* Don't copy here but swap, because when anext is
|
|
* removed below, it must contain the unused context
|
|
*/
|
|
swap_io_context(&arq->io_context, &anext->io_context);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* kill knowledge of next, this one is a goner
|
|
*/
|
|
as_remove_queued_request(q, next);
|
|
as_put_io_context(anext);
|
|
|
|
anext->state = AS_RQ_MERGED;
|
|
}
|
|
|
|
/*
|
|
* This is executed in a "deferred" process context, by kblockd. It calls the
|
|
* driver's request_fn so the driver can submit that request.
|
|
*
|
|
* IMPORTANT! This guy will reenter the elevator, so set up all queue global
|
|
* state before calling, and don't rely on any state over calls.
|
|
*
|
|
* FIXME! dispatch queue is not a queue at all!
|
|
*/
|
|
static void as_work_handler(void *data)
|
|
{
|
|
struct request_queue *q = data;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(q->queue_lock, flags);
|
|
if (!as_queue_empty(q))
|
|
q->request_fn(q);
|
|
spin_unlock_irqrestore(q->queue_lock, flags);
|
|
}
|
|
|
|
static void as_put_request(request_queue_t *q, struct request *rq)
|
|
{
|
|
struct as_data *ad = q->elevator->elevator_data;
|
|
struct as_rq *arq = RQ_DATA(rq);
|
|
|
|
if (!arq) {
|
|
WARN_ON(1);
|
|
return;
|
|
}
|
|
|
|
if (unlikely(arq->state != AS_RQ_POSTSCHED &&
|
|
arq->state != AS_RQ_PRESCHED &&
|
|
arq->state != AS_RQ_MERGED)) {
|
|
printk("arq->state %d\n", arq->state);
|
|
WARN_ON(1);
|
|
}
|
|
|
|
mempool_free(arq, ad->arq_pool);
|
|
rq->elevator_private = NULL;
|
|
}
|
|
|
|
static int as_set_request(request_queue_t *q, struct request *rq,
|
|
struct bio *bio, gfp_t gfp_mask)
|
|
{
|
|
struct as_data *ad = q->elevator->elevator_data;
|
|
struct as_rq *arq = mempool_alloc(ad->arq_pool, gfp_mask);
|
|
|
|
if (arq) {
|
|
memset(arq, 0, sizeof(*arq));
|
|
RB_CLEAR(&arq->rb_node);
|
|
arq->request = rq;
|
|
arq->state = AS_RQ_PRESCHED;
|
|
arq->io_context = NULL;
|
|
INIT_LIST_HEAD(&arq->hash);
|
|
arq->on_hash = 0;
|
|
INIT_LIST_HEAD(&arq->fifo);
|
|
rq->elevator_private = arq;
|
|
return 0;
|
|
}
|
|
|
|
return 1;
|
|
}
|
|
|
|
static int as_may_queue(request_queue_t *q, int rw, struct bio *bio)
|
|
{
|
|
int ret = ELV_MQUEUE_MAY;
|
|
struct as_data *ad = q->elevator->elevator_data;
|
|
struct io_context *ioc;
|
|
if (ad->antic_status == ANTIC_WAIT_REQ ||
|
|
ad->antic_status == ANTIC_WAIT_NEXT) {
|
|
ioc = as_get_io_context();
|
|
if (ad->io_context == ioc)
|
|
ret = ELV_MQUEUE_MUST;
|
|
put_io_context(ioc);
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
static void as_exit_queue(elevator_t *e)
|
|
{
|
|
struct as_data *ad = e->elevator_data;
|
|
|
|
del_timer_sync(&ad->antic_timer);
|
|
kblockd_flush();
|
|
|
|
BUG_ON(!list_empty(&ad->fifo_list[REQ_SYNC]));
|
|
BUG_ON(!list_empty(&ad->fifo_list[REQ_ASYNC]));
|
|
|
|
mempool_destroy(ad->arq_pool);
|
|
put_io_context(ad->io_context);
|
|
kfree(ad->hash);
|
|
kfree(ad);
|
|
}
|
|
|
|
/*
|
|
* initialize elevator private data (as_data), and alloc a arq for
|
|
* each request on the free lists
|
|
*/
|
|
static int as_init_queue(request_queue_t *q, elevator_t *e)
|
|
{
|
|
struct as_data *ad;
|
|
int i;
|
|
|
|
if (!arq_pool)
|
|
return -ENOMEM;
|
|
|
|
ad = kmalloc_node(sizeof(*ad), GFP_KERNEL, q->node);
|
|
if (!ad)
|
|
return -ENOMEM;
|
|
memset(ad, 0, sizeof(*ad));
|
|
|
|
ad->q = q; /* Identify what queue the data belongs to */
|
|
|
|
ad->hash = kmalloc_node(sizeof(struct list_head)*AS_HASH_ENTRIES,
|
|
GFP_KERNEL, q->node);
|
|
if (!ad->hash) {
|
|
kfree(ad);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
ad->arq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
|
|
mempool_free_slab, arq_pool, q->node);
|
|
if (!ad->arq_pool) {
|
|
kfree(ad->hash);
|
|
kfree(ad);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
/* anticipatory scheduling helpers */
|
|
ad->antic_timer.function = as_antic_timeout;
|
|
ad->antic_timer.data = (unsigned long)q;
|
|
init_timer(&ad->antic_timer);
|
|
INIT_WORK(&ad->antic_work, as_work_handler, q);
|
|
|
|
for (i = 0; i < AS_HASH_ENTRIES; i++)
|
|
INIT_LIST_HEAD(&ad->hash[i]);
|
|
|
|
INIT_LIST_HEAD(&ad->fifo_list[REQ_SYNC]);
|
|
INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]);
|
|
ad->sort_list[REQ_SYNC] = RB_ROOT;
|
|
ad->sort_list[REQ_ASYNC] = RB_ROOT;
|
|
ad->fifo_expire[REQ_SYNC] = default_read_expire;
|
|
ad->fifo_expire[REQ_ASYNC] = default_write_expire;
|
|
ad->antic_expire = default_antic_expire;
|
|
ad->batch_expire[REQ_SYNC] = default_read_batch_expire;
|
|
ad->batch_expire[REQ_ASYNC] = default_write_batch_expire;
|
|
e->elevator_data = ad;
|
|
|
|
ad->current_batch_expires = jiffies + ad->batch_expire[REQ_SYNC];
|
|
ad->write_batch_count = ad->batch_expire[REQ_ASYNC] / 10;
|
|
if (ad->write_batch_count < 2)
|
|
ad->write_batch_count = 2;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* sysfs parts below
|
|
*/
|
|
struct as_fs_entry {
|
|
struct attribute attr;
|
|
ssize_t (*show)(struct as_data *, char *);
|
|
ssize_t (*store)(struct as_data *, const char *, size_t);
|
|
};
|
|
|
|
static ssize_t
|
|
as_var_show(unsigned int var, char *page)
|
|
{
|
|
return sprintf(page, "%d\n", var);
|
|
}
|
|
|
|
static ssize_t
|
|
as_var_store(unsigned long *var, const char *page, size_t count)
|
|
{
|
|
char *p = (char *) page;
|
|
|
|
*var = simple_strtoul(p, &p, 10);
|
|
return count;
|
|
}
|
|
|
|
static ssize_t as_est_show(struct as_data *ad, char *page)
|
|
{
|
|
int pos = 0;
|
|
|
|
pos += sprintf(page+pos, "%lu %% exit probability\n",
|
|
100*ad->exit_prob/256);
|
|
pos += sprintf(page+pos, "%lu %% probability of exiting without a "
|
|
"cooperating process submitting IO\n",
|
|
100*ad->exit_no_coop/256);
|
|
pos += sprintf(page+pos, "%lu ms new thinktime\n", ad->new_ttime_mean);
|
|
pos += sprintf(page+pos, "%llu sectors new seek distance\n",
|
|
(unsigned long long)ad->new_seek_mean);
|
|
|
|
return pos;
|
|
}
|
|
|
|
#define SHOW_FUNCTION(__FUNC, __VAR) \
|
|
static ssize_t __FUNC(struct as_data *ad, char *page) \
|
|
{ \
|
|
return as_var_show(jiffies_to_msecs((__VAR)), (page)); \
|
|
}
|
|
SHOW_FUNCTION(as_readexpire_show, ad->fifo_expire[REQ_SYNC]);
|
|
SHOW_FUNCTION(as_writeexpire_show, ad->fifo_expire[REQ_ASYNC]);
|
|
SHOW_FUNCTION(as_anticexpire_show, ad->antic_expire);
|
|
SHOW_FUNCTION(as_read_batchexpire_show, ad->batch_expire[REQ_SYNC]);
|
|
SHOW_FUNCTION(as_write_batchexpire_show, ad->batch_expire[REQ_ASYNC]);
|
|
#undef SHOW_FUNCTION
|
|
|
|
#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \
|
|
static ssize_t __FUNC(struct as_data *ad, const char *page, size_t count) \
|
|
{ \
|
|
int ret = as_var_store(__PTR, (page), count); \
|
|
if (*(__PTR) < (MIN)) \
|
|
*(__PTR) = (MIN); \
|
|
else if (*(__PTR) > (MAX)) \
|
|
*(__PTR) = (MAX); \
|
|
*(__PTR) = msecs_to_jiffies(*(__PTR)); \
|
|
return ret; \
|
|
}
|
|
STORE_FUNCTION(as_readexpire_store, &ad->fifo_expire[REQ_SYNC], 0, INT_MAX);
|
|
STORE_FUNCTION(as_writeexpire_store, &ad->fifo_expire[REQ_ASYNC], 0, INT_MAX);
|
|
STORE_FUNCTION(as_anticexpire_store, &ad->antic_expire, 0, INT_MAX);
|
|
STORE_FUNCTION(as_read_batchexpire_store,
|
|
&ad->batch_expire[REQ_SYNC], 0, INT_MAX);
|
|
STORE_FUNCTION(as_write_batchexpire_store,
|
|
&ad->batch_expire[REQ_ASYNC], 0, INT_MAX);
|
|
#undef STORE_FUNCTION
|
|
|
|
static struct as_fs_entry as_est_entry = {
|
|
.attr = {.name = "est_time", .mode = S_IRUGO },
|
|
.show = as_est_show,
|
|
};
|
|
static struct as_fs_entry as_readexpire_entry = {
|
|
.attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR },
|
|
.show = as_readexpire_show,
|
|
.store = as_readexpire_store,
|
|
};
|
|
static struct as_fs_entry as_writeexpire_entry = {
|
|
.attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR },
|
|
.show = as_writeexpire_show,
|
|
.store = as_writeexpire_store,
|
|
};
|
|
static struct as_fs_entry as_anticexpire_entry = {
|
|
.attr = {.name = "antic_expire", .mode = S_IRUGO | S_IWUSR },
|
|
.show = as_anticexpire_show,
|
|
.store = as_anticexpire_store,
|
|
};
|
|
static struct as_fs_entry as_read_batchexpire_entry = {
|
|
.attr = {.name = "read_batch_expire", .mode = S_IRUGO | S_IWUSR },
|
|
.show = as_read_batchexpire_show,
|
|
.store = as_read_batchexpire_store,
|
|
};
|
|
static struct as_fs_entry as_write_batchexpire_entry = {
|
|
.attr = {.name = "write_batch_expire", .mode = S_IRUGO | S_IWUSR },
|
|
.show = as_write_batchexpire_show,
|
|
.store = as_write_batchexpire_store,
|
|
};
|
|
|
|
static struct attribute *default_attrs[] = {
|
|
&as_est_entry.attr,
|
|
&as_readexpire_entry.attr,
|
|
&as_writeexpire_entry.attr,
|
|
&as_anticexpire_entry.attr,
|
|
&as_read_batchexpire_entry.attr,
|
|
&as_write_batchexpire_entry.attr,
|
|
NULL,
|
|
};
|
|
|
|
#define to_as(atr) container_of((atr), struct as_fs_entry, attr)
|
|
|
|
static ssize_t
|
|
as_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
|
|
{
|
|
elevator_t *e = container_of(kobj, elevator_t, kobj);
|
|
struct as_fs_entry *entry = to_as(attr);
|
|
|
|
if (!entry->show)
|
|
return -EIO;
|
|
|
|
return entry->show(e->elevator_data, page);
|
|
}
|
|
|
|
static ssize_t
|
|
as_attr_store(struct kobject *kobj, struct attribute *attr,
|
|
const char *page, size_t length)
|
|
{
|
|
elevator_t *e = container_of(kobj, elevator_t, kobj);
|
|
struct as_fs_entry *entry = to_as(attr);
|
|
|
|
if (!entry->store)
|
|
return -EIO;
|
|
|
|
return entry->store(e->elevator_data, page, length);
|
|
}
|
|
|
|
static struct sysfs_ops as_sysfs_ops = {
|
|
.show = as_attr_show,
|
|
.store = as_attr_store,
|
|
};
|
|
|
|
static struct kobj_type as_ktype = {
|
|
.sysfs_ops = &as_sysfs_ops,
|
|
.default_attrs = default_attrs,
|
|
};
|
|
|
|
static struct elevator_type iosched_as = {
|
|
.ops = {
|
|
.elevator_merge_fn = as_merge,
|
|
.elevator_merged_fn = as_merged_request,
|
|
.elevator_merge_req_fn = as_merged_requests,
|
|
.elevator_dispatch_fn = as_dispatch_request,
|
|
.elevator_add_req_fn = as_add_request,
|
|
.elevator_activate_req_fn = as_activate_request,
|
|
.elevator_deactivate_req_fn = as_deactivate_request,
|
|
.elevator_queue_empty_fn = as_queue_empty,
|
|
.elevator_completed_req_fn = as_completed_request,
|
|
.elevator_former_req_fn = as_former_request,
|
|
.elevator_latter_req_fn = as_latter_request,
|
|
.elevator_set_req_fn = as_set_request,
|
|
.elevator_put_req_fn = as_put_request,
|
|
.elevator_may_queue_fn = as_may_queue,
|
|
.elevator_init_fn = as_init_queue,
|
|
.elevator_exit_fn = as_exit_queue,
|
|
},
|
|
|
|
.elevator_ktype = &as_ktype,
|
|
.elevator_name = "anticipatory",
|
|
.elevator_owner = THIS_MODULE,
|
|
};
|
|
|
|
static int __init as_init(void)
|
|
{
|
|
int ret;
|
|
|
|
arq_pool = kmem_cache_create("as_arq", sizeof(struct as_rq),
|
|
0, 0, NULL, NULL);
|
|
if (!arq_pool)
|
|
return -ENOMEM;
|
|
|
|
ret = elv_register(&iosched_as);
|
|
if (!ret) {
|
|
/*
|
|
* don't allow AS to get unregistered, since we would have
|
|
* to browse all tasks in the system and release their
|
|
* as_io_context first
|
|
*/
|
|
__module_get(THIS_MODULE);
|
|
return 0;
|
|
}
|
|
|
|
kmem_cache_destroy(arq_pool);
|
|
return ret;
|
|
}
|
|
|
|
static void __exit as_exit(void)
|
|
{
|
|
elv_unregister(&iosched_as);
|
|
kmem_cache_destroy(arq_pool);
|
|
}
|
|
|
|
module_init(as_init);
|
|
module_exit(as_exit);
|
|
|
|
MODULE_AUTHOR("Nick Piggin");
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_DESCRIPTION("anticipatory IO scheduler");
|