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[PATCH] cfq-iosched: Don't set the queue batching limits

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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: Jens Axboe <axboe@suse.de>
This commit is contained in:
Jens Axboe 2006-06-13 08:08:38 +02:00 committed by Jens Axboe
parent acf4217555
commit 271f18f102
1 changed files with 3 additions and 45 deletions
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48
block/cfq-iosched.c
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@ -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;
struct request_list *rl = &q->rq;
if (cfqq->allocated[READ] <= cfqd->max_queued || cfqd->rq_starved) {
if (unlikely(cfqd->rq_starved)) {
struct request_list *rl = &q->rq;
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;