[PATCH 5/9] block/cfq: Replace cfq_rb_root leftmost caching

Davidlohr Bueso
2017-06-29T17:17:24Z

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

Cc: axboe@fb.com
Cc: linux-block@vger.kernel.org
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
This is part of the rbtree internal caching series:
https://lkml.org/lkml/2017/6/8/857

block/cfq-iosched.c | 70 +++++++++++++++--------------------------------------
1 file changed, 20 insertions(+), 50 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 3d5c28945719..92c31683a2bb 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -93,13 +93,12 @@ struct cfq_ttime {
* move this into the elevator for the rq sorting as well.
*/
struct cfq_rb_root {
- struct rb_root rb;
- struct rb_node *left;
+ struct rb_root_cached rb;
unsigned count;
u64 min_vdisktime;
struct cfq_ttime ttime;
};
-#define CFQ_RB_ROOT (struct cfq_rb_root) { .rb = RB_ROOT, \
+#define CFQ_RB_ROOT (struct cfq_rb_root) { .rb = RB_ROOT_CACHED, \
.ttime = {.last_end_request = ktime_get_ns(),},}

/*
@@ -984,10 +983,9 @@ static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)

static void update_min_vdisktime(struct cfq_rb_root *st)
{
- struct cfq_group *cfqg;
+ if (!RB_EMPTY_ROOT(&st->rb.rb_root)) {
+ struct cfq_group *cfqg = rb_entry_cfqg(st->rb.rb_leftmost);

- if (st->left) {
- cfqg = rb_entry_cfqg(st->left);
st->min_vdisktime = max_vdisktime(st->min_vdisktime,
cfqg->vdisktime);
}
@@ -1169,46 +1167,25 @@ cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2,
}
}

-/*
- * The below is leftmost cache rbtree addon
- */
static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
{
/* Service tree is empty */
if (!root->count)
return NULL;

- if (!root->left)
- root->left = rb_first(&root->rb);
-
- if (root->left)
- return rb_entry(root->left, struct cfq_queue, rb_node);
-
- return NULL;
+ return rb_entry(rb_first_cached(&root->rb), struct cfq_queue, rb_node);
}

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_cfqg(root->left);
-
- return NULL;
+ return rb_entry_cfqg(rb_first_cached(&root->rb));
}

-static void rb_erase_init(struct rb_node *n, struct rb_root *root)
+static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
{
- rb_erase(n, root);
+ rb_erase_cached(n, &root->rb);
RB_CLEAR_NODE(n);
-}

-static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
-{
- if (root->left == n)
- root->left = NULL;
- rb_erase_init(n, &root->rb);
--root->count;
}

@@ -1258,11 +1235,11 @@ cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
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 **node = &st->rb.rb_root.rb_node;
struct rb_node *parent = NULL;
struct cfq_group *__cfqg;
s64 key = cfqg_key(st, cfqg);
- int left = 1;
+ bool leftmost = true;

while (*node != NULL) {
parent = *node;
@@ -1272,15 +1249,12 @@ __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
node = &parent->rb_left;
else {
node = &parent->rb_right;
- left = 0;
+ leftmost = false;
}
}

- if (left)
- st->left = &cfqg->rb_node;
-
rb_link_node(&cfqg->rb_node, parent, node);
- rb_insert_color(&cfqg->rb_node, &st->rb);
+ rb_insert_color_cached(&cfqg->rb_node, &st->rb, leftmost);
}

/*
@@ -1381,7 +1355,7 @@ cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
* so that groups get lesser vtime based on their weights, so that
* if group does not loose all if it was not continuously backlogged.
*/
- n = rb_last(&st->rb);
+ n = rb_last(&st->rb.rb_root);
if (n) {
__cfqg = rb_entry_cfqg(n);
cfqg->vdisktime = __cfqg->vdisktime +
@@ -2223,14 +2197,14 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct cfq_queue *__cfqq;
u64 rb_key;
struct cfq_rb_root *st;
- int left;
+ bool leftmost = true;
int new_cfqq = 1;
u64 now = ktime_get_ns();

st = st_for(cfqq->cfqg, cfqq_class(cfqq), cfqq_type(cfqq));
if (cfq_class_idle(cfqq)) {
rb_key = CFQ_IDLE_DELAY;
- parent = rb_last(&st->rb);
+ parent = rb_last(&st->rb.rb_root);
if (parent && parent != &cfqq->rb_node) {
__cfqq = rb_entry(parent, struct cfq_queue, rb_node);
rb_key += __cfqq->rb_key;
@@ -2264,10 +2238,9 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
cfqq->service_tree = NULL;
}

- left = 1;
parent = NULL;
cfqq->service_tree = st;
- p = &st->rb.rb_node;
+ p = &st->rb.rb_root.rb_node;
while (*p) {
parent = *p;
__cfqq = rb_entry(parent, struct cfq_queue, rb_node);
@@ -2279,16 +2252,13 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
p = &parent->rb_left;
else {
p = &parent->rb_right;
- left = 0;
+ leftmost = false;
}
}

- if (left)
- st->left = &cfqq->rb_node;
-
cfqq->rb_key = rb_key;
rb_link_node(&cfqq->rb_node, parent, p);
- rb_insert_color(&cfqq->rb_node, &st->rb);
+ rb_insert_color_cached(&cfqq->rb_node, &st->rb, leftmost);
st->count++;
if (add_front || !new_cfqq)
return;
@@ -2735,7 +2705,7 @@ static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
/* There is nothing to dispatch */
if (!st)
return NULL;
- if (RB_EMPTY_ROOT(&st->rb))
+ if (RB_EMPTY_ROOT(&st->rb.rb_root))
return NULL;
return cfq_rb_first(st);
}
@@ -3221,7 +3191,7 @@ static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
struct cfq_rb_root *st = &cfqd->grp_service_tree;
struct cfq_group *cfqg;

- if (RB_EMPTY_ROOT(&st->rb))
+ if (RB_EMPTY_ROOT(&st->rb.rb_root))
return NULL;
cfqg = cfq_rb_first_group(st);
update_min_vdisktime(st);
--
2.12.0