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From: Jens Axboe <[email protected]>
To: [email protected], [email protected],
	[email protected]
Cc: Jens Axboe <[email protected]>, Christoph Hellwig <[email protected]>
Subject: [PATCH 1/4] block: add mq_ops->queue_rqs hook
Date: Thu, 16 Dec 2021 09:05:34 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

If we have a list of requests in our plug list, send it to the driver in
one go, if possible. The driver must set mq_ops->queue_rqs() to support
this, if not the usual one-by-one path is used.

Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
---
 block/blk-mq.c         | 26 +++++++++++++++++++++++---
 include/linux/blk-mq.h |  8 ++++++++
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 75154cc788db..51991232824a 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2553,6 +2553,7 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 {
 	struct blk_mq_hw_ctx *this_hctx;
 	struct blk_mq_ctx *this_ctx;
+	struct request *rq;
 	unsigned int depth;
 	LIST_HEAD(list);
 
@@ -2561,7 +2562,28 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 	plug->rq_count = 0;
 
 	if (!plug->multiple_queues && !plug->has_elevator && !from_schedule) {
-		struct request_queue *q = rq_list_peek(&plug->mq_list)->q;
+		struct request_queue *q;
+
+		rq = rq_list_peek(&plug->mq_list);
+		q = rq->q;
+
+		/*
+		 * Peek first request and see if we have a ->queue_rqs() hook.
+		 * If we do, we can dispatch the whole plug list in one go. We
+		 * already know at this point that all requests belong to the
+		 * same queue, caller must ensure that's the case.
+		 *
+		 * Since we pass off the full list to the driver at this point,
+		 * we do not increment the active request count for the queue.
+		 * Bypass shared tags for now because of that.
+		 */
+		if (q->mq_ops->queue_rqs &&
+		    !(rq->mq_hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
+			blk_mq_run_dispatch_ops(q,
+				q->mq_ops->queue_rqs(&plug->mq_list));
+			if (rq_list_empty(plug->mq_list))
+				return;
+		}
 
 		blk_mq_run_dispatch_ops(q,
 				blk_mq_plug_issue_direct(plug, false));
@@ -2573,8 +2595,6 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 	this_ctx = NULL;
 	depth = 0;
 	do {
-		struct request *rq;
-
 		rq = rq_list_pop(&plug->mq_list);
 
 		if (!this_hctx) {
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 772f8f921526..550996cf419c 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -492,6 +492,14 @@ struct blk_mq_ops {
 	 */
 	void (*commit_rqs)(struct blk_mq_hw_ctx *);
 
+	/**
+	 * @queue_rqs: Queue a list of new requests. Driver is guaranteed
+	 * that each request belongs to the same queue. If the driver doesn't
+	 * empty the @rqlist completely, then the rest will be queued
+	 * individually by the block layer upon return.
+	 */
+	void (*queue_rqs)(struct request **rqlist);
+
 	/**
 	 * @get_budget: Reserve budget before queue request, once .queue_rq is
 	 * run, it is driver's responsibility to release the
-- 
2.34.1


  reply	other threads:[~2021-12-16 16:05 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-16 16:05 [PATCHSET v4 0/4] Add support for list issue Jens Axboe
2021-12-16 16:05 ` Jens Axboe [this message]
2021-12-16 16:05 ` [PATCH 2/4] nvme: split command copy into a helper Jens Axboe
2021-12-16 16:05 ` [PATCH 3/4] nvme: separate command prep and issue Jens Axboe
2021-12-16 16:05 ` [PATCH 4/4] nvme: add support for mq_ops->queue_rqs() Jens Axboe
2021-12-16 16:11   ` [PATCH v2 " Jens Axboe
  -- strict thread matches above, loose matches on Subject: below --
2021-12-16 16:38 [PATCHSET v5 0/4] Add support for list issue Jens Axboe
2021-12-16 16:38 ` [PATCH 1/4] block: add mq_ops->queue_rqs hook Jens Axboe
2021-12-15 16:24 [PATCHSET v3 0/4] Add support for list issue Jens Axboe
2021-12-15 16:24 ` [PATCH 1/4] block: add mq_ops->queue_rqs hook Jens Axboe
2021-12-16  9:01   ` Christoph Hellwig
2021-12-20 20:36   ` Keith Busch
2021-12-20 20:47     ` Jens Axboe

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