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cfq-iosched: abstract out the 'may this cfqq dispatch' logic

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Makes the whole thing easier to read, cfq_dispatch_requests() was
a bit messy before.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe 2009-10-06 20:49:37 +02:00
parent 1b59dd511b
commit 0b182d617e
1 changed files with 67 additions and 54 deletions
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121
block/cfq-iosched.c
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@ -1247,67 +1247,21 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd)
return dispatched;
}
/*
* Dispatch a request from cfqq, moving them to the request queue
* dispatch list.
*/
static void cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
struct request *rq;
BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
/*
* follow expired path, else get first next available
*/
rq = cfq_check_fifo(cfqq);
if (!rq)
rq = cfqq->next_rq;
/*
* insert request into driver dispatch list
*/
cfq_dispatch_insert(cfqd->queue, rq);
if (!cfqd->active_cic) {
struct cfq_io_context *cic = RQ_CIC(rq);
atomic_long_inc(&cic->ioc->refcount);
cfqd->active_cic = cic;
}
}
/*
* Find the cfqq that we need to service and move a request from that to the
* dispatch list
*/
static int cfq_dispatch_requests(struct request_queue *q, int force)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_queue *cfqq;
unsigned int max_dispatch;
if (!cfqd->busy_queues)
return 0;
if (unlikely(force))
return cfq_forced_dispatch(cfqd);
cfqq = cfq_select_queue(cfqd);
if (!cfqq)
return 0;
/*
* Drain async requests before we start sync IO
*/
if (cfq_cfqq_idle_window(cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
return 0;
return false;
/*
* If this is an async queue and we have sync IO in flight, let it wait
*/
if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
return 0;
return false;
max_dispatch = cfqd->cfq_quantum;
if (cfq_class_idle(cfqq))
@ -1321,13 +1275,13 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
* idle queue must always only have a single IO in flight
*/
if (cfq_class_idle(cfqq))
return 0;
return false;
/*
* We have other queues, don't allow more IO from this one
*/
if (cfqd->busy_queues > 1)
return 0;
return false;
/*
* Sole queue user, allow bigger slice
@ -1351,13 +1305,72 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
max_dispatch = depth;
}
if (cfqq->dispatched >= max_dispatch)
/*
* If we're below the current max, allow a dispatch
*/
return cfqq->dispatched < max_dispatch;
}
/*
* Dispatch a request from cfqq, moving them to the request queue
* dispatch list.
*/
static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
struct request *rq;
BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
if (!cfq_may_dispatch(cfqd, cfqq))
return false;
/*
* follow expired path, else get first next available
*/
rq = cfq_check_fifo(cfqq);
if (!rq)
rq = cfqq->next_rq;
/*
* insert request into driver dispatch list
*/
cfq_dispatch_insert(cfqd->queue, rq);
if (!cfqd->active_cic) {
struct cfq_io_context *cic = RQ_CIC(rq);
atomic_long_inc(&cic->ioc->refcount);
cfqd->active_cic = cic;
}
return true;
}
/*
* Find the cfqq that we need to service and move a request from that to the
* dispatch list
*/
static int cfq_dispatch_requests(struct request_queue *q, int force)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_queue *cfqq;
if (!cfqd->busy_queues)
return 0;
if (unlikely(force))
return cfq_forced_dispatch(cfqd);
cfqq = cfq_select_queue(cfqd);
if (!cfqq)
return 0;
/*
* Dispatch a request from this cfqq
* Dispatch a request from this cfqq, if it is allowed
*/
cfq_dispatch_request(cfqd, cfqq);
if (!cfq_dispatch_request(cfqd, cfqq))
return 0;
cfqq->slice_dispatch++;
cfq_clear_cfqq_must_dispatch(cfqq);