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Commit 271f18f1 authored by Jens Axboe's avatar Jens Axboe Committed by Jens Axboe
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[PATCH] cfq-iosched: Don't set the queue batching limits 



We cannot update them if the user changes nr_requests, so don't
set it in the first place. The gains are pretty questionable as
well. The batching loss has been shown to decrease throughput.

Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent acf42175

block/cfq-iosched.c

+3 −45
Original line number Diff line number Diff line
@@ -123,8 +123,6 @@ struct cfq_data { 
	 */

	struct hlist_head *crq_hash;



	unsigned int max_queued;



	mempool_t *crq_pool;



	int rq_in_driver;
@@ -1910,7 +1908,6 @@ static inline int 
__cfq_may_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq,

		struct task_struct *task, int rw)

{

#if 1

	if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&

	    !cfq_cfqq_must_alloc_slice(cfqq)) {

		cfq_mark_cfqq_must_alloc_slice(cfqq);
@@ -1918,39 +1915,6 @@ __cfq_may_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	}



	return ELV_MQUEUE_MAY;

#else

	if (!cfqq || task->flags & PF_MEMALLOC)

		return ELV_MQUEUE_MAY;

	if (!cfqq->allocated[rw] || cfq_cfqq_must_alloc(cfqq)) {

		if (cfq_cfqq_wait_request(cfqq))

			return ELV_MQUEUE_MUST;



		/*

		 * only allow 1 ELV_MQUEUE_MUST per slice, otherwise we

		 * can quickly flood the queue with writes from a single task

		 */

		if (rw == READ || !cfq_cfqq_must_alloc_slice(cfqq)) {

			cfq_mark_cfqq_must_alloc_slice(cfqq);

			return ELV_MQUEUE_MUST;

		}



		return ELV_MQUEUE_MAY;

	}

	if (cfq_class_idle(cfqq))

		return ELV_MQUEUE_NO;

	if (cfqq->allocated[rw] >= cfqd->max_queued) {

		struct io_context *ioc = get_io_context(GFP_ATOMIC);

		int ret = ELV_MQUEUE_NO;



		if (ioc && ioc->nr_batch_requests)

			ret = ELV_MQUEUE_MAY;



		put_io_context(ioc);

		return ret;

	}



	return ELV_MQUEUE_MAY;

#endif

}



static int cfq_may_queue(request_queue_t *q, int rw, struct bio *bio)
@@ -1979,16 +1943,13 @@ static int cfq_may_queue(request_queue_t *q, int rw, struct bio *bio) 
static void cfq_check_waiters(request_queue_t *q, struct cfq_queue *cfqq)

{

	struct cfq_data *cfqd = q->elevator->elevator_data;



	if (unlikely(cfqd->rq_starved)) {

		struct request_list *rl = &q->rq;



	if (cfqq->allocated[READ] <= cfqd->max_queued || cfqd->rq_starved) {

		smp_mb();

		if (waitqueue_active(&rl->wait[READ]))

			wake_up(&rl->wait[READ]);

	}



	if (cfqq->allocated[WRITE] <= cfqd->max_queued || cfqd->rq_starved) {

		smp_mb();

		if (waitqueue_active(&rl->wait[WRITE]))

			wake_up(&rl->wait[WRITE]);

	}
@@ -2278,9 +2239,6 @@ static void *cfq_init_queue(request_queue_t *q, elevator_t *e) 


	cfqd->queue = q;



	cfqd->max_queued = q->nr_requests / 4;

	q->nr_batching = cfq_queued;



	init_timer(&cfqd->idle_slice_timer);

	cfqd->idle_slice_timer.function = cfq_idle_slice_timer;

	cfqd->idle_slice_timer.data = (unsigned long) cfqd;