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[BLOCK] ll_rw_blk: fastpath get_request()

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Originally from: Nick Piggin <nickpiggin@yahoo.com.au>

Move current_io_context out of the get_request fastpth.  Also try to
streamline a few other things in this area.

Signed-off-by: Jens Axboe <axboe@suse.de>
This commit is contained in:
Jens Axboe 2005-11-12 11:09:12 +01:00 • committed by Jens Axboe
parent ef9be1d336
commit 88ee5ef157
1 changed files with 37 additions and 33 deletions
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70
block/ll_rw_blk.c
View file

@ -1908,40 +1908,40 @@ static struct request *get_request(request_queue_t *q, int rw, struct bio *bio,
{ {
struct request *rq = NULL; struct request *rq = NULL;
struct request_list *rl = &q->rq; struct request_list *rl = &q->rq;
struct io_context *ioc = current_io_context(GFP_ATOMIC); struct io_context *ioc = NULL;
int priv; int may_queue, priv;
if (rl->count[rw]+1 >= q->nr_requests) { may_queue = elv_may_queue(q, rw, bio);
/* if (may_queue == ELV_MQUEUE_NO)
* The queue will fill after this allocation, so set it as goto rq_starved;
* full, and mark this process as "batching". This process
* will be allowed to complete a batch of requests, others if (rl->count[rw]+1 >= queue_congestion_on_threshold(q)) {
* will be blocked. if (rl->count[rw]+1 >= q->nr_requests) {
*/ ioc = current_io_context(GFP_ATOMIC);
if (!blk_queue_full(q, rw)) { /*
ioc_set_batching(q, ioc); * The queue will fill after this allocation, so set
blk_set_queue_full(q, rw); * it as full, and mark this process as "batching".
* This process will be allowed to complete a batch of
* requests, others will be blocked.
*/
if (!blk_queue_full(q, rw)) {
ioc_set_batching(q, ioc);
blk_set_queue_full(q, rw);
} else {
if (may_queue != ELV_MQUEUE_MUST
&& !ioc_batching(q, ioc)) {
/*
* The queue is full and the allocating
* process is not a "batcher", and not
* exempted by the IO scheduler
*/
goto out;
}
}
} }
set_queue_congested(q, rw);
} }
switch (elv_may_queue(q, rw, bio)) {
case ELV_MQUEUE_NO:
goto rq_starved;
case ELV_MQUEUE_MAY:
break;
case ELV_MQUEUE_MUST:
goto get_rq;
}
if (blk_queue_full(q, rw) && !ioc_batching(q, ioc)) {
/*
* The queue is full and the allocating process is not a
* "batcher", and not exempted by the IO scheduler
*/
goto out;
}
get_rq:
/* /*
* Only allow batching queuers to allocate up to 50% over the defined * Only allow batching queuers to allocate up to 50% over the defined
* limit of requests, otherwise we could have thousands of requests * limit of requests, otherwise we could have thousands of requests
@ -1952,8 +1952,6 @@ static struct request *get_request(request_queue_t *q, int rw, struct bio *bio,
rl->count[rw]++; rl->count[rw]++;
rl->starved[rw] = 0; rl->starved[rw] = 0;
if (rl->count[rw] >= queue_congestion_on_threshold(q))
set_queue_congested(q, rw);
priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags); priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
if (priv) if (priv)
@ -1962,7 +1960,7 @@ static struct request *get_request(request_queue_t *q, int rw, struct bio *bio,
spin_unlock_irq(q->queue_lock); spin_unlock_irq(q->queue_lock);
rq = blk_alloc_request(q, rw, bio, priv, gfp_mask); rq = blk_alloc_request(q, rw, bio, priv, gfp_mask);
if (!rq) { if (unlikely(!rq)) {
/* /*
* Allocation failed presumably due to memory. Undo anything * Allocation failed presumably due to memory. Undo anything
* we might have messed up. * we might have messed up.
@ -1987,6 +1985,12 @@ static struct request *get_request(request_queue_t *q, int rw, struct bio *bio,
goto out; goto out;
} }
/*
* ioc may be NULL here, and ioc_batching will be false. That's
* OK, if the queue is under the request limit then requests need
* not count toward the nr_batch_requests limit. There will always
* be some limit enforced by BLK_BATCH_TIME.
*/
if (ioc_batching(q, ioc)) if (ioc_batching(q, ioc))
ioc->nr_batch_requests--; ioc->nr_batch_requests--;