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Commit f0f1a45f authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Linus Torvalds
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block/cfq: cache rightmost rb_node 

For the same reasons we already cache the leftmost pointer, apply the same
optimization for rb_last() calls.  Users must explicitly do this as
rb_root_cached only deals with the smallest node.

[dave@stgolabs.net: brain fart #1]
  Link: http://lkml.kernel.org/r/20170731155955.GD21328@linux-80c1.suse
Link: http://lkml.kernel.org/r/20170719014603.19029-18-dave@stgolabs.net


Signed-off-by: default avatarDavidlohr Bueso <dbueso@suse.de>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fa90b2fd

block/cfq-iosched.c

+14 −5
Original line number Diff line number Diff line
@@ -94,11 +94,13 @@ struct cfq_ttime { 
 */

struct cfq_rb_root {

	struct rb_root_cached rb;

	struct rb_node *rb_rightmost;

	unsigned count;

	u64 min_vdisktime;

	struct cfq_ttime ttime;

};

#define CFQ_RB_ROOT	(struct cfq_rb_root) { .rb = RB_ROOT_CACHED, \

			.rb_rightmost = NULL,			     \

			.ttime = {.last_end_request = ktime_get_ns(),},}



/*
@@ -1180,6 +1182,9 @@ static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root) 


static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)

{

	if (root->rb_rightmost == n)

		root->rb_rightmost = rb_prev(n);



	rb_erase_cached(n, &root->rb);

	RB_CLEAR_NODE(n);
@@ -1236,20 +1241,24 @@ __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg) 
	struct rb_node *parent = NULL;

	struct cfq_group *__cfqg;

	s64 key = cfqg_key(st, cfqg);

	bool leftmost = true;

	bool leftmost = true, rightmost = true;



	while (*node != NULL) {

		parent = *node;

		__cfqg = rb_entry_cfqg(parent);



		if (key < cfqg_key(st, __cfqg))

		if (key < cfqg_key(st, __cfqg)) {

			node = &parent->rb_left;

		else {

			rightmost = false;

		} else {

			node = &parent->rb_right;

			leftmost = false;

		}

	}



	if (rightmost)

		st->rb_rightmost = &cfqg->rb_node;



	rb_link_node(&cfqg->rb_node, parent, node);

	rb_insert_color_cached(&cfqg->rb_node, &st->rb, leftmost);

}
@@ -1352,7 +1361,7 @@ 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.rb_root);

	n = st->rb_rightmost;

	if (n) {

		__cfqg = rb_entry_cfqg(n);

		cfqg->vdisktime = __cfqg->vdisktime +
@@ -2201,7 +2210,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	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.rb_root);

		parent = st->rb_rightmost;

		if (parent && parent != &cfqq->rb_node) {

			__cfqq = rb_entry(parent, struct cfq_queue, rb_node);

			rb_key += __cfqq->rb_key;