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blk-mq: split make request handler for multi and single queue

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We want slightly different behavior from them:

- On single queue devices, we currently use the per-process plug
  for deferred IO and for merging.

- On multi queue devices, we don't use the per-process plug, but
  we want to go straight to hardware for SYNC IO.

Split blk_mq_make_request() into a blk_sq_make_request() for single
queue devices, and retain blk_mq_make_request() for multi queue
devices. Then we don't need multiple checks for q->nr_hw_queues
in the request mapping.

Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2014-05-22 10:40:51 -06:00
parent 484b4061e6
commit 07068d5b8e
1 changed files with 158 additions and 51 deletions
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209
block/blk-mq.c
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@ -1072,43 +1072,57 @@ static void blk_mq_bio_to_request(struct request *rq, struct bio *bio)
blk_account_io_start(rq, 1);
}
static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
static inline bool blk_mq_merge_queue_io(struct blk_mq_hw_ctx *hctx,
struct blk_mq_ctx *ctx,
struct request *rq, struct bio *bio)
{
struct request_queue *q = hctx->queue;
if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE)) {
blk_mq_bio_to_request(rq, bio);
spin_lock(&ctx->lock);
insert_rq:
__blk_mq_insert_request(hctx, rq, false);
spin_unlock(&ctx->lock);
return false;
} else {
spin_lock(&ctx->lock);
if (!blk_mq_attempt_merge(q, ctx, bio)) {
blk_mq_bio_to_request(rq, bio);
goto insert_rq;
}
spin_unlock(&ctx->lock);
__blk_mq_free_request(hctx, ctx, rq);
return true;
}
}
struct blk_map_ctx {
struct blk_mq_hw_ctx *hctx;
struct blk_mq_ctx *ctx;
};
static struct request *blk_mq_map_request(struct request_queue *q,
struct bio *bio,
struct blk_map_ctx *data)
{
struct blk_mq_hw_ctx *hctx;
struct blk_mq_ctx *ctx;
const int is_sync = rw_is_sync(bio->bi_rw);
const int is_flush_fua = bio->bi_rw & (REQ_FLUSH | REQ_FUA);
int rw = bio_data_dir(bio);
struct request *rq;
unsigned int use_plug, request_count = 0;
int rw = bio_data_dir(bio);
/*
* If we have multiple hardware queues, just go directly to
* one of those for sync IO.
*/
use_plug = !is_flush_fua && ((q->nr_hw_queues == 1) || !is_sync);
blk_queue_bounce(q, &bio);
if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
if (unlikely(blk_mq_queue_enter(q))) {
bio_endio(bio, -EIO);
return;
}
if (use_plug && !blk_queue_nomerges(q) &&
blk_attempt_plug_merge(q, bio, &request_count))
return;
if (blk_mq_queue_enter(q)) {
bio_endio(bio, -EIO);
return;
return NULL;
}
ctx = blk_mq_get_ctx(q);
hctx = q->mq_ops->map_queue(q, ctx->cpu);
if (is_sync)
if (rw_is_sync(bio->bi_rw))
rw |= REQ_SYNC;
trace_block_getrq(q, bio, rw);
rq = __blk_mq_alloc_request(hctx, ctx, GFP_ATOMIC, false);
if (likely(rq))
@ -1123,6 +1137,109 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
}
hctx->queued++;
data->hctx = hctx;
data->ctx = ctx;
return rq;
}
/*
* Multiple hardware queue variant. This will not use per-process plugs,
* but will attempt to bypass the hctx queueing if we can go straight to
* hardware for SYNC IO.
*/
static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
{
const int is_sync = rw_is_sync(bio->bi_rw);
const int is_flush_fua = bio->bi_rw & (REQ_FLUSH | REQ_FUA);
struct blk_map_ctx data;
struct request *rq;
blk_queue_bounce(q, &bio);
if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
bio_endio(bio, -EIO);
return;
}
rq = blk_mq_map_request(q, bio, &data);
if (unlikely(!rq))
return;
if (unlikely(is_flush_fua)) {
blk_mq_bio_to_request(rq, bio);
blk_insert_flush(rq);
goto run_queue;
}
if (is_sync) {
int ret;
blk_mq_bio_to_request(rq, bio);
blk_mq_start_request(rq, true);
/*
* For OK queue, we are done. For error, kill it. Any other
* error (busy), just add it to our list as we previously
* would have done
*/
ret = q->mq_ops->queue_rq(data.hctx, rq);
if (ret == BLK_MQ_RQ_QUEUE_OK)
goto done;
else {
__blk_mq_requeue_request(rq);
if (ret == BLK_MQ_RQ_QUEUE_ERROR) {
rq->errors = -EIO;
blk_mq_end_io(rq, rq->errors);
goto done;
}
}
}
if (!blk_mq_merge_queue_io(data.hctx, data.ctx, rq, bio)) {
/*
* For a SYNC request, send it to the hardware immediately. For
* an ASYNC request, just ensure that we run it later on. The
* latter allows for merging opportunities and more efficient
* dispatching.
*/
run_queue:
blk_mq_run_hw_queue(data.hctx, !is_sync || is_flush_fua);
}
done:
blk_mq_put_ctx(data.ctx);
}
/*
* Single hardware queue variant. This will attempt to use any per-process
* plug for merging and IO deferral.
*/
static void blk_sq_make_request(struct request_queue *q, struct bio *bio)
{
const int is_sync = rw_is_sync(bio->bi_rw);
const int is_flush_fua = bio->bi_rw & (REQ_FLUSH | REQ_FUA);
unsigned int use_plug, request_count = 0;
struct blk_map_ctx data;
struct request *rq;
/*
* If we have multiple hardware queues, just go directly to
* one of those for sync IO.
*/
use_plug = !is_flush_fua && !is_sync;
blk_queue_bounce(q, &bio);
if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
bio_endio(bio, -EIO);
return;
}
if (use_plug && !blk_queue_nomerges(q) &&
blk_attempt_plug_merge(q, bio, &request_count))
return;
rq = blk_mq_map_request(q, bio, &data);
if (unlikely(is_flush_fua)) {
blk_mq_bio_to_request(rq, bio);
@ -1147,37 +1264,23 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
trace_block_plug(q);
}
list_add_tail(&rq->queuelist, &plug->mq_list);
blk_mq_put_ctx(ctx);
blk_mq_put_ctx(data.ctx);
return;
}
}
if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE)) {
blk_mq_bio_to_request(rq, bio);
spin_lock(&ctx->lock);
insert_rq:
__blk_mq_insert_request(hctx, rq, false);
spin_unlock(&ctx->lock);
} else {
spin_lock(&ctx->lock);
if (!blk_mq_attempt_merge(q, ctx, bio)) {
blk_mq_bio_to_request(rq, bio);
goto insert_rq;
}
spin_unlock(&ctx->lock);
__blk_mq_free_request(hctx, ctx, rq);
if (!blk_mq_merge_queue_io(data.hctx, data.ctx, rq, bio)) {
/*
* For a SYNC request, send it to the hardware immediately. For
* an ASYNC request, just ensure that we run it later on. The
* latter allows for merging opportunities and more efficient
* dispatching.
*/
run_queue:
blk_mq_run_hw_queue(data.hctx, !is_sync || is_flush_fua);
}
/*
* For a SYNC request, send it to the hardware immediately. For an
* ASYNC request, just ensure that we run it later on. The latter
* allows for merging opportunities and more efficient dispatching.
*/
run_queue:
blk_mq_run_hw_queue(hctx, !is_sync || is_flush_fua);
blk_mq_put_ctx(ctx);
blk_mq_put_ctx(data.ctx);
}
/*
@ -1670,7 +1773,11 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
q->sg_reserved_size = INT_MAX;
blk_queue_make_request(q, blk_mq_make_request);
if (q->nr_hw_queues > 1)
blk_queue_make_request(q, blk_mq_make_request);
else
blk_queue_make_request(q, blk_sq_make_request);
blk_queue_rq_timed_out(q, blk_mq_rq_timed_out);
if (set->timeout)
blk_queue_rq_timeout(q, set->timeout);