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Commit 41cad6ab authored by Tejun Heo's avatar Tejun Heo
Browse files

cfq-iosched: convert cfq_group_slice() to use cfqg->vfraction 



cfq_group_slice() calculates slice by taking a fraction of
cfq_target_latency according to the ratio of cfqg->weight against
service_tree->total_weight.  This currently works only because all
cfqgs are treated to be at the same level.

To prepare for proper hierarchy support, convert cfq_group_slice() to
base the calculation on cfqg->vfraction.  As cfqg->vfraction is always
a fraction of 1 and represents the fraction allocated to the cfqg with
hierarchy considered, the slice can be simply calculated by
multiplying cfqg->vfraction to cfq_target_latency (with fixed point
shift factored in).

As vfraction calculation currently treats all non-root cfqgs as
children of the root cfqg, this patch doesn't introduce noticeable
behavior difference.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarVivek Goyal <vgoyal@redhat.com>
parent 1d3650f7

block/cfq-iosched.c

+1 −6
Original line number Original line Diff line number Diff line
@@ -85,7 +85,6 @@ struct cfq_rb_root { 
	struct rb_root rb;

	struct rb_root rb;

	struct rb_node *left;

	struct rb_node *left;

	unsigned count;

	unsigned count;

	unsigned total_weight;

	u64 min_vdisktime;

	u64 min_vdisktime;

	struct cfq_ttime ttime;

	struct cfq_ttime ttime;

};

};
@@ -979,9 +978,7 @@ static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd, 
static inline unsigned

static inline unsigned

cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)

cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)

{

{

	struct cfq_rb_root *st = &cfqd->grp_service_tree;

	return cfqd->cfq_target_latency * cfqg->vfraction >> CFQ_SERVICE_SHIFT;



	return cfqd->cfq_target_latency * cfqg->weight / st->total_weight;

}

}





static inline unsigned

static inline unsigned
@@ -1273,7 +1270,6 @@ cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg) 




	cfq_update_group_weight(cfqg);

	cfq_update_group_weight(cfqg);

	__cfq_group_service_tree_add(st, cfqg);

	__cfq_group_service_tree_add(st, cfqg);

	st->total_weight += cfqg->weight;





	/*

	/*

	 * Activate @cfqg and calculate the portion of vfraction @cfqg is

	 * Activate @cfqg and calculate the portion of vfraction @cfqg is
@@ -1360,7 +1356,6 @@ cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg) 
	}

	}





	/* remove from the service tree */

	/* remove from the service tree */

	st->total_weight -= cfqg->weight;

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

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

		cfq_rb_erase(&cfqg->rb_node, st);

		cfq_rb_erase(&cfqg->rb_node, st);

}

}