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block: wire-up support for passthrough plugging 

Add support for plugging in passthrough path. When plugging is enabled, the
requests are added to a plug instead of getting dispatched to the driver.
And when the plug is finished, the whole batch gets dispatched via
->queue_rqs which turns out to be more efficient. Otherwise dispatching
used to happen via ->queue_rq, one request at a time.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220511054750.20432-3-joshi.k@samsung.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2022-05-11 11:17:46 +05:30
parent ee692a21e9
commit 1c2d2fff6d
1 changed files with 39 additions and 34 deletions
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73
block/blk-mq.c
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@ -2340,6 +2340,40 @@ void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
blk_mq_hctx_mark_pending(hctx, ctx);
}
/*
* Allow 2x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple
* queues. This is important for md arrays to benefit from merging
* requests.
*/
static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)
{
if (plug->multiple_queues)
return BLK_MAX_REQUEST_COUNT * 2;
return BLK_MAX_REQUEST_COUNT;
}
static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
{
struct request *last = rq_list_peek(&plug->mq_list);
if (!plug->rq_count) {
trace_block_plug(rq->q);
} else if (plug->rq_count >= blk_plug_max_rq_count(plug) ||
(!blk_queue_nomerges(rq->q) &&
blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
blk_mq_flush_plug_list(plug, false);
trace_block_plug(rq->q);
}
if (!plug->multiple_queues && last && last->q != rq->q)
plug->multiple_queues = true;
if (!plug->has_elevator && (rq->rq_flags & RQF_ELV))
plug->has_elevator = true;
rq->rq_next = NULL;
rq_list_add(&plug->mq_list, rq);
plug->rq_count++;
}
/**
* blk_mq_request_bypass_insert - Insert a request at dispatch list.
* @rq: Pointer to request to be inserted.
@ -2353,7 +2387,12 @@ void blk_mq_request_bypass_insert(struct request *rq, bool at_head,
bool run_queue)
{
struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
struct blk_plug *plug = current->plug;
if (plug) {
blk_add_rq_to_plug(plug, rq);
return;
}
spin_lock(&hctx->lock);
if (at_head)
list_add(&rq->queuelist, &hctx->dispatch);
@ -2676,40 +2715,6 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
hctx->queue->mq_ops->commit_rqs(hctx);
}
/*
* Allow 2x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple
* queues. This is important for md arrays to benefit from merging
* requests.
*/
static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)
{
if (plug->multiple_queues)
return BLK_MAX_REQUEST_COUNT * 2;
return BLK_MAX_REQUEST_COUNT;
}
static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
{
struct request *last = rq_list_peek(&plug->mq_list);
if (!plug->rq_count) {
trace_block_plug(rq->q);
} else if (plug->rq_count >= blk_plug_max_rq_count(plug) ||
(!blk_queue_nomerges(rq->q) &&
blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
blk_mq_flush_plug_list(plug, false);
trace_block_plug(rq->q);
}
if (!plug->multiple_queues && last && last->q != rq->q)
plug->multiple_queues = true;
if (!plug->has_elevator && (rq->rq_flags & RQF_ELV))
plug->has_elevator = true;
rq->rq_next = NULL;
rq_list_add(&plug->mq_list, rq);
plug->rq_count++;
}
static bool blk_mq_attempt_bio_merge(struct request_queue *q,
struct bio *bio, unsigned int nr_segs)
{