block: change the request allocation/congestion logic to be sync/async based

This makes sure that we never wait on async IO for sync requests, instead
of doing the split on writes vs reads.

Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Jens Axboe 2009-04-06 14:48:01 +02:00 • committed by Linus Torvalds
commit 1faa16d228
6 changed files with 102 additions and 84 deletions

View file

@ -484,11 +484,11 @@ static int blk_init_free_list(struct request_queue *q)
{
struct request_list *rl = &q->rq;
rl->count[READ] = rl->count[WRITE] = 0;
rl->starved[READ] = rl->starved[WRITE] = 0;
rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
rl->elvpriv = 0;
init_waitqueue_head(&rl->wait[READ]);
init_waitqueue_head(&rl->wait[WRITE]);
init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
mempool_free_slab, request_cachep, q->node);
@ -699,18 +699,18 @@ static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
ioc->last_waited = jiffies;
}
static void __freed_request(struct request_queue *q, int rw)
static void __freed_request(struct request_queue *q, int sync)
{
struct request_list *rl = &q->rq;
if (rl->count[rw] < queue_congestion_off_threshold(q))
blk_clear_queue_congested(q, rw);
if (rl->count[sync] < queue_congestion_off_threshold(q))
blk_clear_queue_congested(q, sync);
if (rl->count[rw] + 1 <= q->nr_requests) {
if (waitqueue_active(&rl->wait[rw]))
wake_up(&rl->wait[rw]);
if (rl->count[sync] + 1 <= q->nr_requests) {
if (waitqueue_active(&rl->wait[sync]))
wake_up(&rl->wait[sync]);
blk_clear_queue_full(q, rw);
blk_clear_queue_full(q, sync);
}
}
@ -718,18 +718,18 @@ static void __freed_request(struct request_queue *q, int rw)
* A request has just been released. Account for it, update the full and
* congestion status, wake up any waiters. Called under q->queue_lock.
*/
static void freed_request(struct request_queue *q, int rw, int priv)
static void freed_request(struct request_queue *q, int sync, int priv)
{
struct request_list *rl = &q->rq;
rl->count[rw]--;
rl->count[sync]--;
if (priv)
rl->elvpriv--;
__freed_request(q, rw);
__freed_request(q, sync);
if (unlikely(rl->starved[rw ^ 1]))
__freed_request(q, rw ^ 1);
if (unlikely(rl->starved[sync ^ 1]))
__freed_request(q, sync ^ 1);
}
/*
@ -743,15 +743,15 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
struct request *rq = NULL;
struct request_list *rl = &q->rq;
struct io_context *ioc = NULL;
const int rw = rw_flags & 0x01;
const bool is_sync = rw_is_sync(rw_flags) != 0;
int may_queue, priv;
may_queue = elv_may_queue(q, rw_flags);
if (may_queue == ELV_MQUEUE_NO)
goto rq_starved;
if (rl->count[rw]+1 >= queue_congestion_on_threshold(q)) {
if (rl->count[rw]+1 >= q->nr_requests) {
if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
if (rl->count[is_sync]+1 >= q->nr_requests) {
ioc = current_io_context(GFP_ATOMIC, q->node);
/*
* The queue will fill after this allocation, so set
@ -759,9 +759,9 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
* This process will be allowed to complete a batch of
* requests, others will be blocked.
*/
if (!blk_queue_full(q, rw)) {
if (!blk_queue_full(q, is_sync)) {
ioc_set_batching(q, ioc);
blk_set_queue_full(q, rw);
blk_set_queue_full(q, is_sync);
} else {
if (may_queue != ELV_MQUEUE_MUST
&& !ioc_batching(q, ioc)) {
@ -774,7 +774,7 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
}
}
}
blk_set_queue_congested(q, rw);
blk_set_queue_congested(q, is_sync);
}
/*
@ -782,11 +782,11 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
* limit of requests, otherwise we could have thousands of requests
* allocated with any setting of ->nr_requests
*/
if (rl->count[rw] >= (3 * q->nr_requests / 2))
if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
goto out;
rl->count[rw]++;
rl->starved[rw] = 0;
rl->count[is_sync]++;
rl->starved[is_sync] = 0;
priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
if (priv)
@ -804,7 +804,7 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
* wait queue, but this is pretty rare.
*/
spin_lock_irq(q->queue_lock);
freed_request(q, rw, priv);
freed_request(q, is_sync, priv);
/*
* in the very unlikely event that allocation failed and no
@ -814,8 +814,8 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
* rq mempool into READ and WRITE
*/
rq_starved:
if (unlikely(rl->count[rw] == 0))
rl->starved[rw] = 1;
if (unlikely(rl->count[is_sync] == 0))
rl->starved[is_sync] = 1;
goto out;
}
@ -829,7 +829,7 @@ rq_starved:
if (ioc_batching(q, ioc))
ioc->nr_batch_requests--;
trace_block_getrq(q, bio, rw);
trace_block_getrq(q, bio, rw_flags & 1);
out:
return rq;
}
@ -843,7 +843,7 @@ out:
static struct request *get_request_wait(struct request_queue *q, int rw_flags,
struct bio *bio)
{
const int rw = rw_flags & 0x01;
const bool is_sync = rw_is_sync(rw_flags) != 0;
struct request *rq;
rq = get_request(q, rw_flags, bio, GFP_NOIO);
@ -852,10 +852,10 @@ static struct request *get_request_wait(struct request_queue *q, int rw_flags,
struct io_context *ioc;
struct request_list *rl = &q->rq;
prepare_to_wait_exclusive(&rl->wait[rw], &wait,
prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
TASK_UNINTERRUPTIBLE);
trace_block_sleeprq(q, bio, rw);
trace_block_sleeprq(q, bio, rw_flags & 1);
__generic_unplug_device(q);
spin_unlock_irq(q->queue_lock);
@ -871,7 +871,7 @@ static struct request *get_request_wait(struct request_queue *q, int rw_flags,
ioc_set_batching(q, ioc);
spin_lock_irq(q->queue_lock);
finish_wait(&rl->wait[rw], &wait);
finish_wait(&rl->wait[is_sync], &wait);
rq = get_request(q, rw_flags, bio, GFP_NOIO);
};
@ -1070,14 +1070,14 @@ void __blk_put_request(struct request_queue *q, struct request *req)
* it didn't come out of our reserved rq pools
*/
if (req->cmd_flags & REQ_ALLOCED) {
int rw = rq_data_dir(req);
int is_sync = rq_is_sync(req) != 0;
int priv = req->cmd_flags & REQ_ELVPRIV;
BUG_ON(!list_empty(&req->queuelist));
BUG_ON(!hlist_unhashed(&req->hash));
blk_free_request(q, req);
freed_request(q, rw, priv);
freed_request(q, is_sync, priv);
}
}
EXPORT_SYMBOL_GPL(__blk_put_request);

View file

@ -48,28 +48,28 @@ queue_requests_store(struct request_queue *q, const char *page, size_t count)
q->nr_requests = nr;
blk_queue_congestion_threshold(q);
if (rl->count[READ] >= queue_congestion_on_threshold(q))
blk_set_queue_congested(q, READ);
else if (rl->count[READ] < queue_congestion_off_threshold(q))
blk_clear_queue_congested(q, READ);
if (rl->count[BLK_RW_SYNC] >= queue_congestion_on_threshold(q))
blk_set_queue_congested(q, BLK_RW_SYNC);
else if (rl->count[BLK_RW_SYNC] < queue_congestion_off_threshold(q))
blk_clear_queue_congested(q, BLK_RW_SYNC);
if (rl->count[WRITE] >= queue_congestion_on_threshold(q))
blk_set_queue_congested(q, WRITE);
else if (rl->count[WRITE] < queue_congestion_off_threshold(q))
blk_clear_queue_congested(q, WRITE);
if (rl->count[BLK_RW_ASYNC] >= queue_congestion_on_threshold(q))
blk_set_queue_congested(q, BLK_RW_ASYNC);
else if (rl->count[BLK_RW_ASYNC] < queue_congestion_off_threshold(q))
blk_clear_queue_congested(q, BLK_RW_ASYNC);
if (rl->count[READ] >= q->nr_requests) {
blk_set_queue_full(q, READ);
} else if (rl->count[READ]+1 <= q->nr_requests) {
blk_clear_queue_full(q, READ);
wake_up(&rl->wait[READ]);
if (rl->count[BLK_RW_SYNC] >= q->nr_requests) {
blk_set_queue_full(q, BLK_RW_SYNC);
} else if (rl->count[BLK_RW_SYNC]+1 <= q->nr_requests) {
blk_clear_queue_full(q, BLK_RW_SYNC);
wake_up(&rl->wait[BLK_RW_SYNC]);
}
if (rl->count[WRITE] >= q->nr_requests) {
blk_set_queue_full(q, WRITE);
} else if (rl->count[WRITE]+1 <= q->nr_requests) {
blk_clear_queue_full(q, WRITE);
wake_up(&rl->wait[WRITE]);
if (rl->count[BLK_RW_ASYNC] >= q->nr_requests) {
blk_set_queue_full(q, BLK_RW_ASYNC);
} else if (rl->count[BLK_RW_ASYNC]+1 <= q->nr_requests) {
blk_clear_queue_full(q, BLK_RW_ASYNC);
wake_up(&rl->wait[BLK_RW_ASYNC]);
}
spin_unlock_irq(q->queue_lock);
return ret;

View file

@ -677,7 +677,7 @@ void elv_insert(struct request_queue *q, struct request *rq, int where)
}
if (unplug_it && blk_queue_plugged(q)) {
int nrq = q->rq.count[READ] + q->rq.count[WRITE]
int nrq = q->rq.count[BLK_RW_SYNC] + q->rq.count[BLK_RW_ASYNC]
- q->in_flight;
if (nrq >= q->unplug_thresh)