Commit c2dea2d1 authored by Vasily Tarasov's avatar Vasily Tarasov Committed by Jens Axboe
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cfq: async queue allocation per priority 



If we have two processes with different ioprio_class, but the same
ioprio_data, their async requests will fall into the same queue. I guess
such behavior is not expected, because it's not right to put real-time
requests and best-effort requests in the same queue.

The attached patch fixes the problem by introducing additional *cfqq
fields on cfqd, pointing to per-(class,priority) async queues.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 9a79b227

block/cfq-iosched.c

+44 −12
Original line number Diff line number Diff line
@@ -92,7 +92,11 @@ struct cfq_data { 
	struct cfq_queue *active_queue;

	struct cfq_io_context *active_cic;



	struct cfq_queue *async_cfqq[IOPRIO_BE_NR];

	/*

	 * async queue for each priority case

	 */

	struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];

	struct cfq_queue *async_idle_cfqq;



	struct timer_list idle_class_timer;
@@ -1414,24 +1418,44 @@ out: 
	return cfqq;

}



static struct cfq_queue **

cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)

{

	switch(ioprio_class) {

	case IOPRIO_CLASS_RT:

		return &cfqd->async_cfqq[0][ioprio];

	case IOPRIO_CLASS_BE:

		return &cfqd->async_cfqq[1][ioprio];

	case IOPRIO_CLASS_IDLE:

		return &cfqd->async_idle_cfqq;

	default:

		BUG();

	}

}



static struct cfq_queue *

cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,

	      gfp_t gfp_mask)

{

	const int ioprio = task_ioprio(tsk);

	const int ioprio_class = task_ioprio_class(tsk);

	struct cfq_queue **async_cfqq = NULL;

	struct cfq_queue *cfqq = NULL;



	if (!is_sync)

		cfqq = cfqd->async_cfqq[ioprio];

	if (!is_sync) {

		async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);

		cfqq = *async_cfqq;

	}



	if (!cfqq)

		cfqq = cfq_find_alloc_queue(cfqd, is_sync, tsk, gfp_mask);



	/*

	 * pin the queue now that it's allocated, scheduler exit will prune it

	 */

	if (!is_sync && !cfqd->async_cfqq[ioprio]) {

	if (!is_sync && !(*async_cfqq)) {

		atomic_inc(&cfqq->ref);

		cfqd->async_cfqq[ioprio] = cfqq;

		*async_cfqq = cfqq;

	}



	atomic_inc(&cfqq->ref);
@@ -2042,11 +2066,24 @@ static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) 
	blk_sync_queue(cfqd->queue);

}



static void cfq_put_async_queues(struct cfq_data *cfqd)

{

	int i;



	for (i = 0; i < IOPRIO_BE_NR; i++) {

		if (cfqd->async_cfqq[0][i])

			cfq_put_queue(cfqd->async_cfqq[0][i]);

		if (cfqd->async_cfqq[1][i])

			cfq_put_queue(cfqd->async_cfqq[1][i]);

		if (cfqd->async_idle_cfqq)

			cfq_put_queue(cfqd->async_idle_cfqq);

	}

}



static void cfq_exit_queue(elevator_t *e)

{

	struct cfq_data *cfqd = e->elevator_data;

	request_queue_t *q = cfqd->queue;

	int i;



	cfq_shutdown_timer_wq(cfqd);
@@ -2063,12 +2100,7 @@ static void cfq_exit_queue(elevator_t *e) 
		__cfq_exit_single_io_context(cfqd, cic);

	}



	/*

	 * Put the async queues

	 */

	for (i = 0; i < IOPRIO_BE_NR; i++)

		if (cfqd->async_cfqq[i])	

			cfq_put_queue(cfqd->async_cfqq[i]);

	cfq_put_async_queues(cfqd);



	spin_unlock_irq(q->queue_lock);

include/linux/ioprio.h

+8 −0
Original line number Diff line number Diff line
@@ -53,6 +53,14 @@ static inline int task_ioprio(struct task_struct *task) 
	return IOPRIO_NORM;

}



static inline int task_ioprio_class(struct task_struct *task)

{

	if (ioprio_valid(task->ioprio))

		return IOPRIO_PRIO_CLASS(task->ioprio);



	return IOPRIO_CLASS_BE;

}



static inline int task_nice_ioprio(struct task_struct *task)

{

	return (task_nice(task) + 20) / 5;

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