[PATCH 04/16] blkio: Introduce the root service tree for cfq groups

Vivek Goyal
2009-11-12T23:35:28Z

o So far we just had one cfq_group in cfq_data. To create space for more than
one cfq_group, we need to have a service tree of groups where all the groups
can be queued if they have active cfq queues backlogged in these.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
block/cfq-iosched.c | 137 +++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 134 insertions(+), 3 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index c254917..33c3e62 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -77,8 +77,9 @@ struct cfq_rb_root {
struct rb_root rb;
struct rb_node *left;
unsigned count;
+ u64 min_vdisktime;
};
-#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, }
+#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, 0, }

/*
* Per process-grouping structure
@@ -156,6 +157,16 @@ enum wl_type_t {

/* This is per cgroup per device grouping structure */
struct cfq_group {
+ /* group service_tree member */
+ struct rb_node rb_node;
+
+ /* group service_tree key */
+ u64 vdisktime;
+ bool on_st;
+
+ /* number of cfqq currently on this group */
+ int nr_cfqq;
+
/*
* rr lists of queues with requests, onle rr for each priority class.
* Counts are embedded in the cfq_rb_root
@@ -170,6 +181,8 @@ struct cfq_group {
struct cfq_data {
struct request_queue *queue;

+ /* Root service tree for cfq_groups */
+ struct cfq_rb_root grp_service_tree;
struct cfq_group root_group;

/*
@@ -245,6 +258,9 @@ static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
enum wl_type_t type,
struct cfq_data *cfqd)
{
+ if (!cfqg)
+ return NULL;
+
if (prio == IDLE_WORKLOAD)
return &cfqg->service_tree_idle;

@@ -566,6 +582,17 @@ static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
return NULL;
}

+static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
+{
+ if (!root->left)
+ root->left = rb_first(&root->rb);
+
+ if (root->left)
+ return rb_entry(root->left, struct cfq_group, rb_node);
+
+ return NULL;
+}
+
static void rb_erase_init(struct rb_node *n, struct rb_root *root)
{
rb_erase(n, root);
@@ -617,6 +644,83 @@ static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
}

+static inline s64
+cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
+{
+ return cfqg->vdisktime - st->min_vdisktime;
+}
+
+static void
+__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
+{
+ struct rb_node **node = &st->rb.rb_node;
+ struct rb_node *parent = NULL;
+ struct cfq_group *__cfqg;
+ s64 key = cfqg_key(st, cfqg);
+ int left = 1;
+
+ while (*node != NULL) {
+ parent = *node;
+ __cfqg = rb_entry(parent, struct cfq_group, rb_node);
+
+ if (key < cfqg_key(st, __cfqg))
+ node = &parent->rb_left;
+ else {
+ node = &parent->rb_right;
+ left = 0;
+ }
+ }
+
+ if (left)
+ st->left = &cfqg->rb_node;
+
+ rb_link_node(&cfqg->rb_node, parent, node);
+ rb_insert_color(&cfqg->rb_node, &st->rb);
+}
+
+static void
+cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
+{
+ struct cfq_rb_root *st = &cfqd->grp_service_tree;
+ struct cfq_group *__cfqg;
+ struct rb_node *n;
+
+ cfqg->nr_cfqq++;
+ if (cfqg->on_st)
+ return;
+
+ /*
+ * Currently put the group at the end. Later implement something
+ * so that groups get lesser vtime based on their weights, so that
+ * if group does not loose all if it was not continously backlogged.
+ */
+ n = rb_last(&st->rb);
+ if (n) {
+ __cfqg = rb_entry(n, struct cfq_group, rb_node);
+ cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
+ } else
+ cfqg->vdisktime = st->min_vdisktime;
+
+ __cfq_group_service_tree_add(st, cfqg);
+ cfqg->on_st = true;
+}
+
+static void
+cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
+{
+ struct cfq_rb_root *st = &cfqd->grp_service_tree;
+
+ BUG_ON(cfqg->nr_cfqq < 1);
+ cfqg->nr_cfqq--;
+ /* If there are other cfq queues under this group, don't delete it */
+ if (cfqg->nr_cfqq)
+ return;
+
+ cfqg->on_st = false;
+ if (!RB_EMPTY_NODE(&cfqg->rb_node))
+ cfq_rb_erase(&cfqg->rb_node, st);
+}
+
/*
* The cfqd->service_trees holds all pending cfq_queue's that have
* requests waiting to be processed. It is sorted in the order that
@@ -699,6 +803,7 @@ 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++;
+ cfq_group_service_tree_add(cfqd, cfqq->cfqg);
}

static struct cfq_queue *
@@ -809,6 +914,8 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
cfqq->p_root = NULL;
}

+ cfq_group_service_tree_del(cfqd, cfqq->cfqg);
+
BUG_ON(!cfqd->busy_queues);
cfqd->busy_queues--;
}
@@ -1085,6 +1192,9 @@ static struct cfq_queue *__cfq_get_next_queue(struct cfq_data *cfqd)
if (!cfqd->rq_queued)
return NULL;

+ /* There is nothing to dispatch */
+ if (!service_tree)
+ return NULL;
if (RB_EMPTY_ROOT(&service_tree->rb))
return NULL;
return cfq_rb_first(service_tree);
@@ -1479,6 +1589,12 @@ static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
unsigned count;
struct cfq_rb_root *st;

+ if (!cfqg) {
+ cfqd->serving_prio = IDLE_WORKLOAD;
+ cfqd->workload_expires = jiffies + 1;
+ return;
+ }
+
/* Choose next priority. RT > BE > IDLE */
if (cfq_busy_queues_wl(RT_WORKLOAD, cfqd))
cfqd->serving_prio = RT_WORKLOAD;
@@ -1536,10 +1652,21 @@ static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
cfqd->workload_expires = jiffies + slice;
}

+static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
+{
+ struct cfq_rb_root *st = &cfqd->grp_service_tree;
+
+ if (RB_EMPTY_ROOT(&st->rb))
+ return NULL;
+ return cfq_rb_first_group(st);
+}
+
static void cfq_choose_cfqg(struct cfq_data *cfqd)
{
- cfqd->serving_group = &cfqd->root_group;
- choose_service_tree(cfqd, &cfqd->root_group);
+ struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
+
+ cfqd->serving_group = cfqg;
+ choose_service_tree(cfqd, cfqg);
}

/*
@@ -2995,6 +3122,9 @@ static void *cfq_init_queue(struct request_queue *q)
if (!cfqd)
return NULL;

+ /* Init root service tree */
+ cfqd->grp_service_tree = CFQ_RB_ROOT;
+
/* Init root group */
cfqg = &cfqd->root_group;

@@ -3002,6 +3132,7 @@ static void *cfq_init_queue(struct request_queue *q)
for (j = 0; j < 3; ++j)
cfqg->service_trees[i][j] = CFQ_RB_ROOT;
cfqg->service_tree_idle = CFQ_RB_ROOT;
+ RB_CLEAR_NODE(&cfqg->rb_node);

/*
* Not strictly needed (since RB_ROOT just clears the node and we
--
1.6.2.5