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Commit 597bc485 authored by Jens Axboe's avatar Jens Axboe Committed by Jens Axboe
Browse files

cfq-iosched: speedup cic rb lookup 



We often lookup the same queue many times in succession, so cache
the last looked up queue to avoid browsing the rbtree.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 4e521c27

block/cfq-iosched.c

+18 −2
Original line number Diff line number Diff line
@@ -1165,6 +1165,8 @@ static void cfq_free_io_context(struct io_context *ioc) 
	struct rb_node *n;

	int freed = 0;



	ioc->ioc_data = NULL;



	while ((n = rb_first(&ioc->cic_root)) != NULL) {

		__cic = rb_entry(n, struct cfq_io_context, rb_node);

		rb_erase(&__cic->rb_node, &ioc->cic_root);
@@ -1228,10 +1230,11 @@ static void cfq_exit_io_context(struct io_context *ioc) 
	struct cfq_io_context *__cic;

	struct rb_node *n;



	ioc->ioc_data = NULL;



	/*

	 * put the reference this task is holding to the various queues

	 */



	n = rb_first(&ioc->cic_root);

	while (n != NULL) {

		__cic = rb_entry(n, struct cfq_io_context, rb_node);
@@ -1415,6 +1418,10 @@ static void 
cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)

{

	WARN_ON(!list_empty(&cic->queue_list));



	if (ioc->ioc_data == cic)

		ioc->ioc_data = NULL;



	rb_erase(&cic->rb_node, &ioc->cic_root);

	kmem_cache_free(cfq_ioc_pool, cic);

	elv_ioc_count_dec(ioc_count);
@@ -1430,6 +1437,13 @@ cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc) 
	if (unlikely(!ioc))

		return NULL;



	/*

	 * we maintain a last-hit cache, to avoid browsing over the tree

	 */

	cic = ioc->ioc_data;

	if (cic && cic->key == cfqd)

		return cic;



restart:

	n = ioc->cic_root.rb_node;

	while (n) {
@@ -1445,9 +1459,11 @@ restart: 
			n = n->rb_left;

		else if (key > k)

			n = n->rb_right;

		else

		else {

			ioc->ioc_data = cic;

			return cic;

		}

	}



	return NULL;

}