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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
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+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;