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[BLOCK] as-iosched: update alias handling

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Unlike other ioscheds, as-iosched handles alias by chaing them using
rq->queuelist.  As aliased requests are very rare in the first place,
this complicates merge/dispatch handling without meaningful
performance improvement.  This patch updates as-iosched to dump
aliased requests into dispatch queue as other ioscheds do.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <axboe@suse.de>
This commit is contained in:
Tejun Heo 2005-11-11 14:27:09 +01:00 committed by Jens Axboe
parent 9f155b9802
commit ef9be1d336
1 changed files with 25 additions and 119 deletions
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134
block/as-iosched.c
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@ -182,6 +182,9 @@ struct as_rq {
static kmem_cache_t *arq_pool;
static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq);
static void as_antic_stop(struct as_data *ad);
/*
* IO Context helper functions
*/
@ -370,7 +373,7 @@ static struct as_rq *as_find_first_arq(struct as_data *ad, int data_dir)
* existing request against the same sector), which can happen when using
* direct IO, then return the alias.
*/
static struct as_rq *as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
static struct as_rq *__as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
{
struct rb_node **p = &ARQ_RB_ROOT(ad, arq)->rb_node;
struct rb_node *parent = NULL;
@ -397,6 +400,16 @@ static struct as_rq *as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
return NULL;
}
static void as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
{
struct as_rq *alias;
while ((unlikely(alias = __as_add_arq_rb(ad, arq)))) {
as_move_to_dispatch(ad, alias);
as_antic_stop(ad);
}
}
static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq)
{
if (!ON_RB(&arq->rb_node)) {
@ -1133,23 +1146,6 @@ static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
/*
* take it off the sort and fifo list, add to dispatch queue
*/
while (!list_empty(&rq->queuelist)) {
struct request *__rq = list_entry_rq(rq->queuelist.next);
struct as_rq *__arq = RQ_DATA(__rq);
list_del(&__rq->queuelist);
elv_dispatch_add_tail(ad->q, __rq);
if (__arq->io_context && __arq->io_context->aic)
atomic_inc(&__arq->io_context->aic->nr_dispatched);
WARN_ON(__arq->state != AS_RQ_QUEUED);
__arq->state = AS_RQ_DISPATCHED;
ad->nr_dispatched++;
}
as_remove_queued_request(ad->q, rq);
WARN_ON(arq->state != AS_RQ_QUEUED);
@ -1325,42 +1321,6 @@ fifo_expired:
return 1;
}
/*
* Add arq to a list behind alias
*/
static inline void
as_add_aliased_request(struct as_data *ad, struct as_rq *arq,
struct as_rq *alias)
{
struct request *req = arq->request;
struct list_head *insert = alias->request->queuelist.prev;
/*
* Transfer list of aliases
*/
while (!list_empty(&req->queuelist)) {
struct request *__rq = list_entry_rq(req->queuelist.next);
struct as_rq *__arq = RQ_DATA(__rq);
list_move_tail(&__rq->queuelist, &alias->request->queuelist);
WARN_ON(__arq->state != AS_RQ_QUEUED);
}
/*
* Another request with the same start sector on the rbtree.
* Link this request to that sector. They are untangled in
* as_move_to_dispatch
*/
list_add(&arq->request->queuelist, insert);
/*
* Don't want to have to handle merges.
*/
as_del_arq_hash(arq);
arq->request->flags |= REQ_NOMERGE;
}
/*
* add arq to rbtree and fifo
*/
@ -1368,7 +1328,6 @@ static void as_add_request(request_queue_t *q, struct request *rq)
{
struct as_data *ad = q->elevator->elevator_data;
struct as_rq *arq = RQ_DATA(rq);
struct as_rq *alias;
int data_dir;
arq->state = AS_RQ_NEW;
@ -1387,33 +1346,17 @@ static void as_add_request(request_queue_t *q, struct request *rq)
atomic_inc(&arq->io_context->aic->nr_queued);
}
alias = as_add_arq_rb(ad, arq);
if (!alias) {
as_add_arq_rb(ad, arq);
if (rq_mergeable(arq->request))
as_add_arq_hash(ad, arq);
/*
* set expire time (only used for reads) and add to fifo list
*/
arq->expires = jiffies + ad->fifo_expire[data_dir];
list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]);
if (rq_mergeable(arq->request))
as_add_arq_hash(ad, arq);
as_update_arq(ad, arq); /* keep state machine up to date */
} else {
as_add_aliased_request(ad, arq, alias);
/*
* have we been anticipating this request?
* or does it come from the same process as the one we are
* anticipating for?
*/
if (ad->antic_status == ANTIC_WAIT_REQ
|| ad->antic_status == ANTIC_WAIT_NEXT) {
if (as_can_break_anticipation(ad, arq))
as_antic_stop(ad);
}
}
arq->state = AS_RQ_QUEUED;
}
@ -1536,23 +1479,8 @@ static void as_merged_request(request_queue_t *q, struct request *req)
* if the merge was a front merge, we need to reposition request
*/
if (rq_rb_key(req) != arq->rb_key) {
struct as_rq *alias, *next_arq = NULL;
if (ad->next_arq[arq->is_sync] == arq)
next_arq = as_find_next_arq(ad, arq);
/*
* Note! We should really be moving any old aliased requests
* off this request and try to insert them into the rbtree. We
* currently don't bother. Ditto the next function.
*/
as_del_arq_rb(ad, arq);
if ((alias = as_add_arq_rb(ad, arq))) {
list_del_init(&arq->fifo);
as_add_aliased_request(ad, arq, alias);
if (next_arq)
ad->next_arq[arq->is_sync] = next_arq;
}
as_add_arq_rb(ad, arq);
/*
* Note! At this stage of this and the next function, our next
* request may not be optimal - eg the request may have "grown"
@ -1579,18 +1507,8 @@ static void as_merged_requests(request_queue_t *q, struct request *req,
as_add_arq_hash(ad, arq);
if (rq_rb_key(req) != arq->rb_key) {
struct as_rq *alias, *next_arq = NULL;
if (ad->next_arq[arq->is_sync] == arq)
next_arq = as_find_next_arq(ad, arq);
as_del_arq_rb(ad, arq);
if ((alias = as_add_arq_rb(ad, arq))) {
list_del_init(&arq->fifo);
as_add_aliased_request(ad, arq, alias);
if (next_arq)
ad->next_arq[arq->is_sync] = next_arq;
}
as_add_arq_rb(ad, arq);
}
/*
@ -1609,18 +1527,6 @@ static void as_merged_requests(request_queue_t *q, struct request *req,
}
}
/*
* Transfer list of aliases
*/
while (!list_empty(&next->queuelist)) {
struct request *__rq = list_entry_rq(next->queuelist.next);
struct as_rq *__arq = RQ_DATA(__rq);
list_move_tail(&__rq->queuelist, &req->queuelist);
WARN_ON(__arq->state != AS_RQ_QUEUED);
}
/*
* kill knowledge of next, this one is a goner
*/