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authorTejun Heo <tj@kernel.org>2013-01-09 08:05:11 -0800
committerTejun Heo <tj@kernel.org>2013-01-09 08:05:11 -0800
commitd02f7aa8dce8166dbbc515ce393912aa45e6b8a6 (patch)
tree8a3e8e54bed797bb084a83008ca47065a261a9d6 /block
parent41cad6ab2cb9ccb3b11546ad56b8b285e47c6279 (diff)
downloadlinaro-lsk-d02f7aa8dce8166dbbc515ce393912aa45e6b8a6.tar.gz
cfq-iosched: enable full blkcg hierarchy support
With the previous two patches, all cfqg scheduling decisions are based on vfraction and ready for hierarchy support. The only thing which keeps the behavior flat is cfqg_flat_parent() which makes vfraction calculation consider all non-root cfqgs children of the root cfqg. Replace it with cfqg_parent() which returns the real parent. This enables full blkcg hierarchy support for cfq-iosched. For example, consider the following hierarchy. root / \ A:500 B:250 / \ AA:500 AB:1000 For simplicity, let's say all the leaf nodes have active tasks and are on service tree. For each leaf node, vfraction would be AA: (500 / 1500) * (500 / 750) =~ 0.2222 AB: (1000 / 1500) * (500 / 750) =~ 0.4444 B: (250 / 750) =~ 0.3333 and vdisktime will be distributed accordingly. For more detail, please refer to Documentation/block/cfq-iosched.txt. v2: cfq-iosched.txt updated to describe group scheduling as suggested by Vivek. v3: blkio-controller.txt updated. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com>
Diffstat (limited to 'block')
-rw-r--r--block/cfq-iosched.c21
1 files changed, 6 insertions, 15 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ee342826fd9..e8f31069b37 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -606,20 +606,11 @@ static inline struct cfq_group *blkg_to_cfqg(struct blkcg_gq *blkg)
return pd_to_cfqg(blkg_to_pd(blkg, &blkcg_policy_cfq));
}
-/*
- * Determine the parent cfqg for weight calculation. Currently, cfqg
- * scheduling is flat and the root is the parent of everyone else.
- */
-static inline struct cfq_group *cfqg_flat_parent(struct cfq_group *cfqg)
+static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg)
{
- struct blkcg_gq *blkg = cfqg_to_blkg(cfqg);
- struct cfq_group *root;
-
- while (blkg->parent)
- blkg = blkg->parent;
- root = blkg_to_cfqg(blkg);
+ struct blkcg_gq *pblkg = cfqg_to_blkg(cfqg)->parent;
- return root != cfqg ? root : NULL;
+ return pblkg ? blkg_to_cfqg(pblkg) : NULL;
}
static inline void cfqg_get(struct cfq_group *cfqg)
@@ -722,7 +713,7 @@ static void cfq_pd_reset_stats(struct blkcg_gq *blkg)
#else /* CONFIG_CFQ_GROUP_IOSCHED */
-static inline struct cfq_group *cfqg_flat_parent(struct cfq_group *cfqg) { return NULL; }
+static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg) { return NULL; }
static inline void cfqg_get(struct cfq_group *cfqg) { }
static inline void cfqg_put(struct cfq_group *cfqg) { }
@@ -1290,7 +1281,7 @@ cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
* stops once an already activated node is met. vfraction
* calculation should always continue to the root.
*/
- while ((parent = cfqg_flat_parent(pos))) {
+ while ((parent = cfqg_parent(pos))) {
if (propagate) {
propagate = !parent->nr_active++;
parent->children_weight += pos->weight;
@@ -1341,7 +1332,7 @@ cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
pos->children_weight -= pos->leaf_weight;
while (propagate) {
- struct cfq_group *parent = cfqg_flat_parent(pos);
+ struct cfq_group *parent = cfqg_parent(pos);
/* @pos has 0 nr_active at this point */
WARN_ON_ONCE(pos->children_weight);