[PATCH 3/9] sched/deadline: Replace earliest dl and rq leftmost caching

Davidlohr Bueso
2017-06-29T17:16:50Z

... with the generic rbtree flavor instead. No changes
in semantics whatsoever.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
kernel/sched/deadline.c | 50 +++++++++++++++++++------------------------------
kernel/sched/sched.h | 6 ++----
2 files changed, 21 insertions(+), 35 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index a84299f44b5d..5d2ab09e7b9f 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -296,7 +296,7 @@ static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
{
struct sched_dl_entity *dl_se = &p->dl;

- return dl_rq->rb_leftmost == &dl_se->rb_node;
+ return dl_rq->root.rb_leftmost == &dl_se->rb_node;
}

void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime)
@@ -320,7 +320,7 @@ void init_dl_bw(struct dl_bw *dl_b)

void init_dl_rq(struct dl_rq *dl_rq)
{
- dl_rq->rb_root = RB_ROOT;
+ dl_rq->root = RB_ROOT_CACHED;

#ifdef CONFIG_SMP
/* zero means no -deadline tasks */
@@ -328,7 +328,7 @@ void init_dl_rq(struct dl_rq *dl_rq)

dl_rq->dl_nr_migratory = 0;
dl_rq->overloaded = 0;
- dl_rq->pushable_dl_tasks_root = RB_ROOT;
+ dl_rq->pushable_dl_tasks_root = RB_ROOT_CACHED;
#else
init_dl_bw(&dl_rq->dl_bw);
#endif
@@ -410,10 +410,10 @@ static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
{
struct dl_rq *dl_rq = &rq->dl;
- struct rb_node **link = &dl_rq->pushable_dl_tasks_root.rb_node;
+ struct rb_node **link = &dl_rq->pushable_dl_tasks_root.rb_root.rb_node;
struct rb_node *parent = NULL;
struct task_struct *entry;
- int leftmost = 1;
+ bool leftmost = true;

BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));

@@ -425,17 +425,16 @@ static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
link = &parent->rb_left;
else {
link = &parent->rb_right;
- leftmost = 0;
+ leftmost = false;
}
}

- if (leftmost) {
- dl_rq->pushable_dl_tasks_leftmost = &p->pushable_dl_tasks;
+ if (leftmost)
dl_rq->earliest_dl.next = p->dl.deadline;
- }

rb_link_node(&p->pushable_dl_tasks, parent, link);
- rb_insert_color(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
+ rb_insert_color_cached(&p->pushable_dl_tasks,
+ &dl_rq->pushable_dl_tasks_root, leftmost);
}

static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
@@ -445,24 +444,23 @@ static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
return;

- if (dl_rq->pushable_dl_tasks_leftmost == &p->pushable_dl_tasks) {
+ if (dl_rq->pushable_dl_tasks_root.rb_leftmost == &p->pushable_dl_tasks) {
struct rb_node *next_node;

next_node = rb_next(&p->pushable_dl_tasks);
- dl_rq->pushable_dl_tasks_leftmost = next_node;
if (next_node) {
dl_rq->earliest_dl.next = rb_entry(next_node,
struct task_struct, pushable_dl_tasks)->dl.deadline;
}
}

- rb_erase(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
+ rb_erase_cached(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
RB_CLEAR_NODE(&p->pushable_dl_tasks);
}

static inline int has_pushable_dl_tasks(struct rq *rq)
{
- return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root);
+ return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root.rb_root);
}

static int push_dl_task(struct rq *rq);
@@ -1266,7 +1264,7 @@ static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
dl_rq->earliest_dl.next = 0;
cpudl_clear(&rq->rd->cpudl, rq->cpu);
} else {
- struct rb_node *leftmost = dl_rq->rb_leftmost;
+ struct rb_node *leftmost = dl_rq->root.rb_leftmost;
struct sched_dl_entity *entry;

entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
@@ -1313,7 +1311,7 @@ void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
{
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
- struct rb_node **link = &dl_rq->rb_root.rb_node;
+ struct rb_node **link = &dl_rq->root.rb_root.rb_node;
struct rb_node *parent = NULL;
struct sched_dl_entity *entry;
int leftmost = 1;
@@ -1331,11 +1329,8 @@ static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
}
}

- if (leftmost)
- dl_rq->rb_leftmost = &dl_se->rb_node;
-
rb_link_node(&dl_se->rb_node, parent, link);
- rb_insert_color(&dl_se->rb_node, &dl_rq->rb_root);
+ rb_insert_color_cached(&dl_se->rb_node, &dl_rq->root, leftmost);

inc_dl_tasks(dl_se, dl_rq);
}
@@ -1347,14 +1342,7 @@ static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
if (RB_EMPTY_NODE(&dl_se->rb_node))
return;

- if (dl_rq->rb_leftmost == &dl_se->rb_node) {
- struct rb_node *next_node;
-
- next_node = rb_next(&dl_se->rb_node);
- dl_rq->rb_leftmost = next_node;
- }
-
- rb_erase(&dl_se->rb_node, &dl_rq->rb_root);
+ rb_erase_cached(&dl_se->rb_node, &dl_rq->root);
RB_CLEAR_NODE(&dl_se->rb_node);

dec_dl_tasks(dl_se, dl_rq);
@@ -1645,7 +1633,7 @@ static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
struct dl_rq *dl_rq)
{
- struct rb_node *left = dl_rq->rb_leftmost;
+ struct rb_node *left = rb_first_cached(&dl_rq->root);

if (!left)
return NULL;
@@ -1769,7 +1757,7 @@ static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
*/
static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu)
{
- struct rb_node *next_node = rq->dl.pushable_dl_tasks_leftmost;
+ struct rb_node *next_node = rq->dl.pushable_dl_tasks_root.rb_leftmost;
struct task_struct *p = NULL;

if (!has_pushable_dl_tasks(rq))
@@ -1942,7 +1930,7 @@ static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
if (!has_pushable_dl_tasks(rq))
return NULL;

- p = rb_entry(rq->dl.pushable_dl_tasks_leftmost,
+ p = rb_entry(rq->dl.pushable_dl_tasks_root.rb_leftmost,
struct task_struct, pushable_dl_tasks);

BUG_ON(rq->cpu != task_cpu(p));
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index bf4d3f7d29c7..d34d1a0dd563 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -549,8 +549,7 @@ struct rt_rq {
/* Deadline class' related fields in a runqueue */
struct dl_rq {
/* runqueue is an rbtree, ordered by deadline */
- struct rb_root rb_root;
- struct rb_node *rb_leftmost;
+ struct rb_root_cached root;

unsigned long dl_nr_running;

@@ -574,8 +573,7 @@ struct dl_rq {
* an rb-tree, ordered by tasks' deadlines, with caching
* of the leftmost (earliest deadline) element.
*/
- struct rb_root pushable_dl_tasks_root;
- struct rb_node *pushable_dl_tasks_leftmost;
+ struct rb_root_cached pushable_dl_tasks_root;
#else
struct dl_bw dl_bw;
#endif
--
2.12.0