Re: [PATCH 14/24] cfq-iosched: convert cfq_group_slice() to use cfqg->vfraction
On Fri, Dec 28, 2012 at 12:35:36PM -0800, Tejun Heo wrote: > 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: Tejun Heo Acked-by: Vivek Goyal Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 14/24] cfq-iosched: convert cfq_group_slice() to use cfqg-vfraction
On Fri, Dec 28, 2012 at 12:35:36PM -0800, Tejun Heo wrote: 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: Tejun Heo t...@kernel.org Acked-by: Vivek Goyal vgo...@redhat.com Vivek -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 14/24] 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: Tejun Heo
---
block/cfq-iosched.c | 7 +--
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index b24acf6..ee34282 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -85,7 +85,6 @@ struct cfq_rb_root {
struct rb_root rb;
struct rb_node *left;
unsigned count;
- unsigned total_weight;
u64 min_vdisktime;
struct cfq_ttime ttime;
};
@@ -979,9 +978,7 @@ static inline unsigned cfq_group_get_avg_queues(struct
cfq_data *cfqd,
static inline unsigned
cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
- struct cfq_rb_root *st = >grp_service_tree;
-
- return cfqd->cfq_target_latency * cfqg->weight / st->total_weight;
+ return cfqd->cfq_target_latency * cfqg->vfraction >> CFQ_SERVICE_SHIFT;
}
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_group_service_tree_add(st, cfqg);
- st->total_weight += cfqg->weight;
/*
* 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 */
- st->total_weight -= cfqg->weight;
if (!RB_EMPTY_NODE(>rb_node))
cfq_rb_erase(>rb_node, st);
}
--
1.8.0.2
--
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[PATCH 14/24] 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: Tejun Heo t...@kernel.org
---
block/cfq-iosched.c | 7 +--
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index b24acf6..ee34282 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -85,7 +85,6 @@ struct cfq_rb_root {
struct rb_root rb;
struct rb_node *left;
unsigned count;
- unsigned total_weight;
u64 min_vdisktime;
struct cfq_ttime ttime;
};
@@ -979,9 +978,7 @@ static inline unsigned cfq_group_get_avg_queues(struct
cfq_data *cfqd,
static inline unsigned
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-weight / st-total_weight;
+ return cfqd-cfq_target_latency * cfqg-vfraction CFQ_SERVICE_SHIFT;
}
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_group_service_tree_add(st, cfqg);
- st-total_weight += cfqg-weight;
/*
* 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 */
- st-total_weight -= cfqg-weight;
if (!RB_EMPTY_NODE(cfqg-rb_node))
cfq_rb_erase(cfqg-rb_node, st);
}
--
1.8.0.2
--
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