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Jens Axboe
b4878f245e
This patch updates all four ioscheds to use generic dispatch queue. There's one behavior change in as-iosched. * In as-iosched, when force dispatching (ELEVATOR_INSERT_BACK), batch_data_dir is reset to REQ_SYNC and changed_batch and new_batch are cleared to zero. This prevernts AS from doing incorrect update_write_batch after the forced dispatched requests are finished. * In cfq-iosched, cfqd->rq_in_driver currently counts the number of activated (removed) requests to determine whether queue-kicking is needed and cfq_max_depth has been reached. With generic dispatch queue, I think counting the number of dispatched requests would be more appropriate. * cfq_max_depth can be lowered to 1 again. Original from Tejun Heo, modified version applied. Signed-off-by: Jens Axboe <axboe@suse.de>
77 lines
1.5 KiB
C
77 lines
1.5 KiB
C
/*
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* elevator noop
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*/
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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/module.h>
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#include <linux/init.h>
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/*
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* See if we can find a request that this buffer can be coalesced with.
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*/
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static int elevator_noop_merge(request_queue_t *q, struct request **req,
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struct bio *bio)
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{
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int ret;
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ret = elv_try_last_merge(q, bio);
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if (ret != ELEVATOR_NO_MERGE)
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*req = q->last_merge;
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return ret;
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}
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static void elevator_noop_merge_requests(request_queue_t *q, struct request *req,
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struct request *next)
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{
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list_del_init(&next->queuelist);
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}
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static void elevator_noop_add_request(request_queue_t *q, struct request *rq)
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{
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elv_dispatch_add_tail(q, rq);
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/*
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* new merges must not precede this barrier
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*/
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if (rq->flags & REQ_HARDBARRIER)
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q->last_merge = NULL;
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else if (!q->last_merge)
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q->last_merge = rq;
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}
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static int elevator_noop_dispatch(request_queue_t *q, int force)
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{
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return 0;
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}
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static struct elevator_type elevator_noop = {
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.ops = {
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.elevator_merge_fn = elevator_noop_merge,
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.elevator_merge_req_fn = elevator_noop_merge_requests,
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.elevator_dispatch_fn = elevator_noop_dispatch,
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.elevator_add_req_fn = elevator_noop_add_request,
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},
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.elevator_name = "noop",
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.elevator_owner = THIS_MODULE,
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};
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static int __init noop_init(void)
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{
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return elv_register(&elevator_noop);
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}
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static void __exit noop_exit(void)
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{
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elv_unregister(&elevator_noop);
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}
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module_init(noop_init);
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module_exit(noop_exit);
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MODULE_AUTHOR("Jens Axboe");
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("No-op IO scheduler");
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