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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: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe 2007-04-24 21:23:53 +02:00 committed by Jens Axboe
parent 4e521c27ee
commit 597bc485d6
1 changed files with 18 additions and 2 deletions
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20
block/cfq-iosched.c
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@ -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) {
@ -1445,8 +1459,10 @@ restart:
n = n->rb_left;
else if (key > k)
n = n->rb_right;
else
else {
ioc->ioc_data = cic;
return cic;
}
}
return NULL;