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Commit 8682e1f1 authored by Vivek Goyal's avatar Vivek Goyal Committed by Jens Axboe
Browse files

blkio: Provide some isolation between groups 



o Do not allow following three operations across groups for isolation.
	- selection of co-operating queues
	- preemtpions across groups
	- request merging across groups.

o Async queues are currently global and not per group. Allow preemption of
  an async queue if a sync queue in other group gets backlogged.

Signed-off-by: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 22084190

block/cfq-iosched.c

+20 −10
Original line number Diff line number Diff line
@@ -1461,6 +1461,9 @@ static int cfq_allow_merge(struct request_queue *q, struct request *rq, 
	struct cfq_io_context *cic;

	struct cfq_queue *cfqq;



	/* Deny merge if bio and rq don't belong to same cfq group */

	if ((RQ_CFQQ(rq))->cfqg != cfq_get_cfqg(cfqd, 0))

		return false;

	/*

	 * Disallow merge of a sync bio into an async request.

	 */
@@ -1698,6 +1701,10 @@ static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd, 
	if (!cfqq)

		return NULL;



	/* If new queue belongs to different cfq_group, don't choose it */

	if (cur_cfqq->cfqg != cfqq->cfqg)

		return NULL;



	/*

	 * It only makes sense to merge sync queues.

	 */
@@ -2950,22 +2957,12 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 
	if (!cfqq)

		return false;



	if (cfq_slice_used(cfqq))

		return true;



	if (cfq_class_idle(new_cfqq))

		return false;



	if (cfq_class_idle(cfqq))

		return true;



	/* Allow preemption only if we are idling on sync-noidle tree */

	if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&

	    cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&

	    new_cfqq->service_tree->count == 2 &&

	    RB_EMPTY_ROOT(&cfqq->sort_list))

		return true;



	/*

	 * if the new request is sync, but the currently running queue is

	 * not, let the sync request have priority.
@@ -2973,6 +2970,19 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 
	if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))

		return true;



	if (new_cfqq->cfqg != cfqq->cfqg)

		return false;



	if (cfq_slice_used(cfqq))

		return true;



	/* Allow preemption only if we are idling on sync-noidle tree */

	if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&

	    cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&

	    new_cfqq->service_tree->count == 2 &&

	    RB_EMPTY_ROOT(&cfqq->sort_list))

		return true;



	/*

	 * So both queues are sync. Let the new request get disk time if

	 * it's a metadata request and the current queue is doing regular IO.