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Commit dae739eb authored by Vivek Goyal's avatar Vivek Goyal Committed by Jens Axboe
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blkio: Group time used accounting and workload context save restore 



o This patch introduces the functionality to do the accounting of group time
  when a queue expires. This time used decides which is the group to go
  next.

o Also introduce the functionlity to save and restore the workload type
  context with-in group. It might happen that once we expire the cfq queue
  and group, a different group will schedule in and we will lose the context
  of the workload type. Hence save and restore it upon queue expiry.

Signed-off-by: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 58ff82f3

block/cfq-iosched.c

+79 −0
Original line number Diff line number Diff line
@@ -115,6 +115,10 @@ struct cfq_queue { 
	/* fifo list of requests in sort_list */

	struct list_head fifo;



	/* time when queue got scheduled in to dispatch first request. */

	unsigned long dispatch_start;

	/* time when first request from queue completed and slice started. */

	unsigned long slice_start;

	unsigned long slice_end;

	long slice_resid;

	unsigned int slice_dispatch;
@@ -181,6 +185,10 @@ struct cfq_group { 
	 */

	struct cfq_rb_root service_trees[2][3];

	struct cfq_rb_root service_tree_idle;



	unsigned long saved_workload_slice;

	enum wl_type_t saved_workload;

	enum wl_prio_t saved_serving_prio;

};



/*
@@ -543,6 +551,7 @@ cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 
				    low_slice);

		}

	}

	cfqq->slice_start = jiffies;

	cfqq->slice_end = jiffies + slice;

	cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);

}
@@ -818,6 +827,58 @@ cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg) 
	st->total_weight -= cfqg->weight;

	if (!RB_EMPTY_NODE(&cfqg->rb_node))

		cfq_rb_erase(&cfqg->rb_node, st);

	cfqg->saved_workload_slice = 0;

}



static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)

{

	unsigned int slice_used, allocated_slice;



	/*

	 * Queue got expired before even a single request completed or

	 * got expired immediately after first request completion.

	 */

	if (!cfqq->slice_start || cfqq->slice_start == jiffies) {

		/*

		 * Also charge the seek time incurred to the group, otherwise

		 * if there are mutiple queues in the group, each can dispatch

		 * a single request on seeky media and cause lots of seek time

		 * and group will never know it.

		 */

		slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),

					1);

	} else {

		slice_used = jiffies - cfqq->slice_start;

		allocated_slice = cfqq->slice_end - cfqq->slice_start;

		if (slice_used > allocated_slice)

			slice_used = allocated_slice;

	}



	cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u", slice_used);

	return slice_used;

}



static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,

				struct cfq_queue *cfqq)

{

	struct cfq_rb_root *st = &cfqd->grp_service_tree;

	unsigned int used_sl;



	used_sl = cfq_cfqq_slice_usage(cfqq);



	/* Can't update vdisktime while group is on service tree */

	cfq_rb_erase(&cfqg->rb_node, st);

	cfqg->vdisktime += cfq_scale_slice(used_sl, cfqg);

	__cfq_group_service_tree_add(st, cfqg);



	/* This group is being expired. Save the context */

	if (time_after(cfqd->workload_expires, jiffies)) {

		cfqg->saved_workload_slice = cfqd->workload_expires

						- jiffies;

		cfqg->saved_workload = cfqd->serving_type;

		cfqg->saved_serving_prio = cfqd->serving_prio;

	} else

		cfqg->saved_workload_slice = 0;

}



/*
@@ -833,6 +894,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	unsigned long rb_key;

	struct cfq_rb_root *service_tree;

	int left;

	int new_cfqq = 1;



	service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),

						cfqq_type(cfqq), cfqd);
@@ -861,6 +923,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	}



	if (!RB_EMPTY_NODE(&cfqq->rb_node)) {

		new_cfqq = 0;

		/*

		 * same position, nothing more to do

		 */
@@ -902,6 +965,8 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	rb_link_node(&cfqq->rb_node, parent, p);

	rb_insert_color(&cfqq->rb_node, &service_tree->rb);

	service_tree->count++;

	if (add_front || !new_cfqq)

		return;

	cfq_group_service_tree_add(cfqd, cfqq->cfqg);

}
@@ -1218,6 +1283,8 @@ static void __cfq_set_active_queue(struct cfq_data *cfqd, 
{

	if (cfqq) {

		cfq_log_cfqq(cfqd, cfqq, "set_active");

		cfqq->slice_start = 0;

		cfqq->dispatch_start = jiffies;

		cfqq->slice_end = 0;

		cfqq->slice_dispatch = 0;
@@ -1255,6 +1322,8 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
		cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);

	}



	cfq_group_served(cfqd, cfqq->cfqg, cfqq);



	if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))

		cfq_del_cfqq_rr(cfqd, cfqq);
@@ -1263,6 +1332,9 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	if (cfqq == cfqd->active_queue)

		cfqd->active_queue = NULL;



	if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active)

		cfqd->grp_service_tree.active = NULL;



	if (cfqd->active_cic) {

		put_io_context(cfqd->active_cic->ioc);

		cfqd->active_cic = NULL;
@@ -1747,6 +1819,13 @@ static void cfq_choose_cfqg(struct cfq_data *cfqd) 
	struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);



	cfqd->serving_group = cfqg;



	/* Restore the workload type data */

	if (cfqg->saved_workload_slice) {

		cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;

		cfqd->serving_type = cfqg->saved_workload;

		cfqd->serving_prio = cfqg->saved_serving_prio;

	}

	choose_service_tree(cfqd, cfqg);

}