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block plugging improvements

PATCH New Jens Axboe 5 participants 31 messages Nov 28, 2018 – Dec 4, 2018

Subsystems (4)
Block layer virtio core NVMe virtio block and SCSI drivers
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Jens Axboe

author maintainer
#0 lore raw

v2 cover block plugging improvements

Series improving plugging for fast devices, but some fixes in here too.

Patch 1 changes the logic for when we sort the plug list, switching it to only doing it if we have requests for multiple queues in the plug (and enough requests to warrant an actual sort).

2-6 add a ->commit_rqs() hook and implement it in drivers that use (or will use) bd->last to optimize IO submission. If a driver currently uses bd->last to know if it's needed to kick the hardware into action, there are cases where we flag bd->last == false, but then fail to submit any further IO due to other resource constraints. We probably get saved by the fact that this happens for the case where we have pending IO and that will eventually guarantee forward progress, but we really should kick IO into gear at that point.

7 improves plugging for blk-mq.

In terms of improvements, for virtualized nvme, I've seen a 2-x IOPS improvement with proper handling of bd->last with this series.

Changes since v1:

- Fold the plug case for blk-mq, do it if we have 1 hw queue, or if we have ->commit_rqs().
- Add disable/enable IRQ to ataflop
- Drop nvme ring index helper
- Rework when to sort patch

Signature · 1 line
Jens Axboe
author maintainer
#1 lore raw

PATCH 1/7 block: improve logic around when to sort a plug list

Only do it if we have requests for multiple queues in the same plug.

Signed-off-by Jens Axboe <axboe at kernel.dk>
---
 block/blk-core.c       |  1 +
 block/blk-mq.c         | 23 ++++++++++++++++++-----
 include/linux/blkdev.h |  1 +
 3 files changed, 20 insertions(+), 5 deletions(-)
block/blk-core.c +1 -0
index be9233400314..d107d016b92b 100644
@@ -1780,6 +1780,7 @@ void blk_start_plug(struct blk_plug *plug)
 	INIT_LIST_HEAD(&plug->mq_list);
 	INIT_LIST_HEAD(&plug->cb_list);
 	plug->rq_count = 0;
+	plug->multiple_queues = false;
 
 	/*
 	 * Store ordering should not be needed here, since a potential
block/blk-mq.c +18 -5
index a82830f39933..0e2663048d95 100644
@@ -1677,7 +1677,8 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 	list_splice_init(&plug->mq_list, &list);
 	plug->rq_count = 0;
 
-	list_sort(NULL, &list, plug_rq_cmp);
+	if (plug->rq_count > 2 && plug->multiple_queues)
+		list_sort(NULL, &list, plug_rq_cmp);
 
 	this_q = NULL;
 	this_hctx = NULL;

@@ -1866,6 +1867,20 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
 	}
 }
 
+static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
+{
+	list_add_tail(&rq->queuelist, &plug->mq_list);
+	plug->rq_count++;
+	if (!plug->multiple_queues && !list_is_singular(&plug->mq_list)) {
+		struct request *tmp;
+
+		tmp = list_first_entry(&plug->mq_list, struct request,
+						queuelist);
+		if (tmp->q != rq->q)
+			plug->multiple_queues = true;
+	}
+}
+
 static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 {
 	const int is_sync = op_is_sync(bio->bi_opf);

@@ -1932,8 +1947,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 			trace_block_plug(q);
 		}
 
-		list_add_tail(&rq->queuelist, &plug->mq_list);
-		plug->rq_count++;
+		blk_add_rq_to_plug(plug, rq);
 	} else if (plug && !blk_queue_nomerges(q)) {
 		blk_mq_bio_to_request(rq, bio);
 

@@ -1950,8 +1964,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 			list_del_init(&same_queue_rq->queuelist);
 			plug->rq_count--;
 		}
-		list_add_tail(&rq->queuelist, &plug->mq_list);
-		plug->rq_count++;
+		blk_add_rq_to_plug(plug, rq);
 
 		blk_mq_put_ctx(data.ctx);
include/linux/blkdev.h +1 -0
index 02732cae6080..08d940f85fa0 100644
@@ -1131,6 +1131,7 @@ struct blk_plug {
 	struct list_head mq_list; /* blk-mq requests */
 	struct list_head cb_list; /* md requires an unplug callback */
 	unsigned short rq_count;
+	bool multiple_queues;
 };
 #define BLK_MAX_REQUEST_COUNT 16
 #define BLK_PLUG_FLUSH_SIZE (128 * 1024)
Signature · 1 line
2.17.1
Reviewed-by on v1 1/7
#2 lore raw

Re: [PATCH 1/7] block: improve logic around when to sort a plug list

Looks good,

Reviewed-by Christoph Hellwig <hch at lst.de>
maintainer Reviewed-by on v1 1/7
#3 lore raw

Re: [PATCH 1/7] block: improve logic around when to sort a plug list

In reply to Jens Axboe
Reviewed-by Sagi Grimberg <sagi at grimberg.me>
author maintainer
#4 lore raw

PATCH 2/7 blk-mq: add mq_ops->commit_rqs()

In reply to Jens Axboe

blk-mq passes information to the hardware about any given request being the last that we will issue in this sequence. The point is that hardware can defer costly doorbell type writes to the last request. But if we run into errors issuing a sequence of requests, we may never send the request with bd->last == true set. For that case, we need a hook that tells the hardware that nothing else is coming right now.

For failures returned by the drivers ->queue_rq() hook, the driver is responsible for flushing pending requests, if it uses bd->last to optimize that part. This works like before, no changes there.

Reviewed-by Omar Sandoval <osandov at fb.com>
Reviewed-by Ming Lei <ming.lei at redhat.com>
Reviewed-by Christoph Hellwig <hch at lst.de>
Signed-off-by Jens Axboe <axboe at kernel.dk>
---
 block/blk-mq.c         | 16 ++++++++++++++++
 include/linux/blk-mq.h | 10 ++++++++++
 2 files changed, 26 insertions(+)
block/blk-mq.c +16 -0
index 0e2663048d95..18ff47a85ad3 100644
@@ -1259,6 +1259,14 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
 	if (!list_empty(list)) {
 		bool needs_restart;
 
+		/*
+		 * If we didn't flush the entire list, we could have told
+		 * the driver there was more coming, but that turned out to
+		 * be a lie.
+		 */
+		if (q->mq_ops->commit_rqs)
+			q->mq_ops->commit_rqs(hctx);
+
 		spin_lock(&hctx->lock);
 		list_splice_init(list, &hctx->dispatch);
 		spin_unlock(&hctx->lock);

@@ -1865,6 +1873,14 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
 			blk_mq_end_request(rq, ret);
 		}
 	}
+
+	/*
+	 * If we didn't flush the entire list, we could have told
+	 * the driver there was more coming, but that turned out to
+	 * be a lie.
+	 */
+	if (!list_empty(list) && hctx->queue->mq_ops->commit_rqs)
+		hctx->queue->mq_ops->commit_rqs(hctx);
 }
 
 static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
include/linux/blk-mq.h +10 -0
index b8de11e0603b..467f1dd21ccf 100644
@@ -117,6 +117,7 @@ struct blk_mq_queue_data {
 
 typedef blk_status_t (queue_rq_fn)(struct blk_mq_hw_ctx *,
 		const struct blk_mq_queue_data *);
+typedef void (commit_rqs_fn)(struct blk_mq_hw_ctx *);
 /* takes rq->cmd_flags as input, returns a hardware type index */
 typedef int (rq_flags_to_type_fn)(struct request_queue *, unsigned int);
 typedef bool (get_budget_fn)(struct blk_mq_hw_ctx *);

@@ -144,6 +145,15 @@ struct blk_mq_ops {
 	 */
 	queue_rq_fn		*queue_rq;
 
+	/*
+	 * If a driver uses bd->last to judge when to submit requests to
+	 * hardware, it must define this function. In case of errors that
+	 * make us stop issuing further requests, this hook serves the
+	 * purpose of kicking the hardware (which the last request otherwise
+	 * would have done).
+	 */
+	commit_rqs_fn		*commit_rqs;
+
 	/*
 	 * Return a queue map type for the given request/bio flags
 	 */
Signature · 1 line
2.17.1
Reviewed-by on v1 2/7
#5 lore raw

Re: [PATCH 2/7] blk-mq: add mq_ops->commit_rqs()

Quoted 7 lines · Jens Axboe

blk-mq passes information to the hardware about any given request being the last that we will issue in this sequence. The point is that hardware can defer costly doorbell type writes to the last request. But if we run into errors issuing a sequence of requests, we may never send the request with bd->last == true set. For that case, we need a hook that tells the hardware that nothing else is coming right now.

Quoted 7 lines

For failures returned by the drivers ->queue_rq() hook, the driver is responsible for flushing pending requests, if it uses bd->last to optimize that part. This works like before, no changes there.

Reviewed-by Omar Sandoval <osandov at fb.com>
Reviewed-by Ming Lei <ming.lei at redhat.com>
Reviewed-by Christoph Hellwig <hch at lst.de>

I don't think I actually reviewed it before in this form.

But now that I took a look it does indeed look fine to me:

Reviewed-by Christoph Hellwig <hch at lst.de>
author maintainer
#6 lore raw

Re: [PATCH 2/7] blk-mq: add mq_ops->commit_rqs()

Quoted 16 lines · Christoph Hellwig
Quoted 7 lines · Jens Axboe

blk-mq passes information to the hardware about any given request being the last that we will issue in this sequence. The point is that hardware can defer costly doorbell type writes to the last request. But if we run into errors issuing a sequence of requests, we may never send the request with bd->last == true set. For that case, we need a hook that tells the hardware that nothing else is coming right now.

Quoted 7 lines

For failures returned by the drivers ->queue_rq() hook, the driver is responsible for flushing pending requests, if it uses bd->last to optimize that part. This works like before, no changes there.

Reviewed-by Omar Sandoval <osandov at fb.com>
Reviewed-by Ming Lei <ming.lei at redhat.com>
Reviewed-by Christoph Hellwig <hch at lst.de>
Quoted 5 lines

I don't think I actually reviewed it before in this form.

But now that I took a look it does indeed look fine to me:

Reviewed-by Christoph Hellwig <hch at lst.de>

Only change is moving those two hunks from the later patch into this one, so it isn't an empty declaration.

Signature · 1 line
Jens Axboe
author maintainer
#8 lore raw

PATCH 3/7 nvme: implement mq_ops->commit_rqs() hook

In reply to Jens Axboe

Split the command submission and the SQ doorbell ring, and add the doorbell ring as our ->commit_rqs() hook. This allows a list of requests to be issued, with nvme only writing the SQ update when it's necessary. This is more efficient if we have lists of requests to issue, particularly on virtualized hardware, where writing the SQ doorbell is more expensive than on real hardware. For those cases, performance increases of 2-3x have been observed.

The use case for this is plugged IO, where blk-mq flushes a batch of requests at the time.

Signed-off-by Jens Axboe <axboe at kernel.dk>
---
 drivers/nvme/host/pci.c | 52 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 46 insertions(+), 6 deletions(-)
drivers/nvme/host/pci.c +46 -6
index 73effe586e5f..42472bd0cfed 100644
@@ -203,6 +203,7 @@ struct nvme_queue {
 	u16 q_depth;
 	s16 cq_vector;
 	u16 sq_tail;
+	u16 last_sq_tail;
 	u16 cq_head;
 	u16 last_cq_head;
 	u16 qid;

@@ -522,22 +523,59 @@ static int nvme_pci_map_queues(struct blk_mq_tag_set *set)
 	return 0;
 }
 
+static inline void nvme_write_sq_db(struct nvme_queue *nvmeq)
+{
+	if (nvme_dbbuf_update_and_check_event(nvmeq->sq_tail,
+			nvmeq->dbbuf_sq_db, nvmeq->dbbuf_sq_ei))
+		writel(nvmeq->sq_tail, nvmeq->q_db);
+	nvmeq->last_sq_tail = nvmeq->sq_tail;
+}
+
+static inline int nvme_next_ring_index(struct nvme_queue *nvmeq, u16 index)
+{
+	if (++index == nvmeq->q_depth)
+		return 0;
+
+	return index;
+}
+
 /**
  * nvme_submit_cmd() - Copy a command into a queue and ring the doorbell
  * @nvmeq: The queue to use
  * @cmd: The command to send
+ * @write_sq: whether to write to the SQ doorbell
  */
-static void nvme_submit_cmd(struct nvme_queue *nvmeq, struct nvme_command *cmd)
+static void nvme_submit_cmd(struct nvme_queue *nvmeq, struct nvme_command *cmd,
+			    bool write_sq)
 {
+	u16 next_tail;
+
 	spin_lock(&nvmeq->sq_lock);
 
 	memcpy(&nvmeq->sq_cmds[nvmeq->sq_tail], cmd, sizeof(*cmd));
 
 	if (++nvmeq->sq_tail == nvmeq->q_depth)
 		nvmeq->sq_tail = 0;
-	if (nvme_dbbuf_update_and_check_event(nvmeq->sq_tail,
-			nvmeq->dbbuf_sq_db, nvmeq->dbbuf_sq_ei))
-		writel(nvmeq->sq_tail, nvmeq->q_db);
+
+	next_tail = nvmeq->sq_tail + 1;
+	if (next_tail == nvmeq->q_depth)
+		next_tail = 0;
+
+	/*
+	 * Write sq tail if we have to, OR if the next command would wrap
+	 */
+	if (write_sq || next_tail == nvmeq->last_sq_tail)
+		nvme_write_sq_db(nvmeq);
+	spin_unlock(&nvmeq->sq_lock);
+}
+
+static void nvme_commit_rqs(struct blk_mq_hw_ctx *hctx)
+{
+	struct nvme_queue *nvmeq = hctx->driver_data;
+
+	spin_lock(&nvmeq->sq_lock);
+	if (nvmeq->sq_tail != nvmeq->last_sq_tail)
+		nvme_write_sq_db(nvmeq);
 	spin_unlock(&nvmeq->sq_lock);
 }
 

@@ -923,7 +961,7 @@ static blk_status_t nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
 	}
 
 	blk_mq_start_request(req);
-	nvme_submit_cmd(nvmeq, &cmnd);
+	nvme_submit_cmd(nvmeq, &cmnd, bd->last);
 	return BLK_STS_OK;
 out_cleanup_iod:
 	nvme_free_iod(dev, req);

@@ -1108,7 +1146,7 @@ static void nvme_pci_submit_async_event(struct nvme_ctrl *ctrl)
 	memset(&c, 0, sizeof(c));
 	c.common.opcode = nvme_admin_async_event;
 	c.common.command_id = NVME_AQ_BLK_MQ_DEPTH;
-	nvme_submit_cmd(nvmeq, &c);
+	nvme_submit_cmd(nvmeq, &c, true);
 }
 
 static int adapter_delete_queue(struct nvme_dev *dev, u8 opcode, u16 id)

@@ -1531,6 +1569,7 @@ static void nvme_init_queue(struct nvme_queue *nvmeq, u16 qid)
 
 	spin_lock_irq(&nvmeq->cq_lock);
 	nvmeq->sq_tail = 0;
+	nvmeq->last_sq_tail = 0;
 	nvmeq->cq_head = 0;
 	nvmeq->cq_phase = 1;
 	nvmeq->q_db = &dev->dbs[qid * 2 * dev->db_stride];

@@ -1603,6 +1642,7 @@ static const struct blk_mq_ops nvme_mq_admin_ops = {
 
 #define NVME_SHARED_MQ_OPS					\
 	.queue_rq		= nvme_queue_rq,		\
+	.commit_rqs		= nvme_commit_rqs,		\
 	.rq_flags_to_type	= nvme_rq_flags_to_type,	\
 	.complete		= nvme_pci_complete_rq,		\
 	.init_hctx		= nvme_init_hctx,		\
Signature · 1 line
2.17.1
#9 lore raw

Re: [PATCH 3/7] nvme: implement mq_ops->commit_rqs() hook

Review

Quoted 7 lines
(quoted diff) +7 -0
+static inline int nvme_next_ring_index(struct nvme_queue *nvmeq, u16 index)
+{
+	if (++index == nvmeq->q_depth)
+		return 0;
+
+	return index;
+}

This is unused now.

Also what about this little cleanup on top?

drivers/nvme/host/pci.c +15 -24
index 42472bd0cfed..527907aa6903 100644
@@ -523,22 +523,26 @@ static int nvme_pci_map_queues(struct blk_mq_tag_set *set)
 	return 0;
 }
 
-static inline void nvme_write_sq_db(struct nvme_queue *nvmeq)
+/*
+ * Write sq tail if we are asked to, or if the next command would wrap.
+ */
+static inline void nvme_write_sq_db(struct nvme_queue *nvmeq, bool write_sq)
 {
+	if (!write_sq) {
+		u16 next_tail = nvmeq->sq_tail + 1;
+
+		if (next_tail == nvmeq->q_depth)
+			next_tail = 0;
+		if (next_tail != nvmeq->last_sq_tail)
+			return;
+	}
+
 	if (nvme_dbbuf_update_and_check_event(nvmeq->sq_tail,
 			nvmeq->dbbuf_sq_db, nvmeq->dbbuf_sq_ei))
 		writel(nvmeq->sq_tail, nvmeq->q_db);
 	nvmeq->last_sq_tail = nvmeq->sq_tail;
 }
 
-static inline int nvme_next_ring_index(struct nvme_queue *nvmeq, u16 index)
-{
-	if (++index == nvmeq->q_depth)
-		return 0;
-
-	return index;
-}
-
 /**
  * nvme_submit_cmd() - Copy a command into a queue and ring the doorbell
  * @nvmeq: The queue to use

@@ -548,24 +552,11 @@ static inline int nvme_next_ring_index(struct nvme_queue *nvmeq, u16 index)
 static void nvme_submit_cmd(struct nvme_queue *nvmeq, struct nvme_command *cmd,
 			    bool write_sq)
 {
-	u16 next_tail;
-
 	spin_lock(&nvmeq->sq_lock);
-
 	memcpy(&nvmeq->sq_cmds[nvmeq->sq_tail], cmd, sizeof(*cmd));
-
 	if (++nvmeq->sq_tail == nvmeq->q_depth)
 		nvmeq->sq_tail = 0;
-
-	next_tail = nvmeq->sq_tail + 1;
-	if (next_tail == nvmeq->q_depth)
-		next_tail = 0;
-
-	/*
-	 * Write sq tail if we have to, OR if the next command would wrap
-	 */
-	if (write_sq || next_tail == nvmeq->last_sq_tail)
-		nvme_write_sq_db(nvmeq);
+	nvme_write_sq_db(nvmeq, write_sq);
 	spin_unlock(&nvmeq->sq_lock);
 }
 

@@ -575,7 +566,7 @@ static void nvme_commit_rqs(struct blk_mq_hw_ctx *hctx)
 
 	spin_lock(&nvmeq->sq_lock);
 	if (nvmeq->sq_tail != nvmeq->last_sq_tail)
-		nvme_write_sq_db(nvmeq);
+		nvme_write_sq_db(nvmeq, true);
 	spin_unlock(&nvmeq->sq_lock);
 }
author maintainer
#10 lore raw

Re: [PATCH 3/7] nvme: implement mq_ops->commit_rqs() hook

Quoted 9 lines · Christoph Hellwig

Review

Quoted 7 lines
(quoted diff) +7 -0
+static inline int nvme_next_ring_index(struct nvme_queue *nvmeq, u16 index)
+{
+	if (++index == nvmeq->q_depth)
+		return 0;
+
+	return index;
+}

This is unused now.

Huh, wonder how I missed that. GCC must not have complained.

Quoted 1 line

Also what about this little cleanup on top?

That looks good, I like it. With that, can I add your reviewed-by? I'll run a sanity check on it first.

Signature · 1 line
Jens Axboe
Reviewed-by
#11 lore raw

Re: [PATCH 3/7] nvme: implement mq_ops->commit_rqs() hook

Quoted 11 lines · Jens Axboe
Quoted 9 lines · Christoph Hellwig

Review

Quoted 7 lines
(quoted diff) +7 -0
+static inline int nvme_next_ring_index(struct nvme_queue *nvmeq, u16 index)
+{
+	if (++index == nvmeq->q_depth)
+		return 0;
+
+	return index;
+}

This is unused now.

Quoted 1 line

Huh, wonder how I missed that. GCC must not have complained.

gcc never warns about unused static inline functions. Which makes a lot of sense at least for headers..

Quoted 5 lines
Quoted 2 lines

Also what about this little cleanup on top?

That looks good, I like it. With that, can I add your reviewed-by? I'll run a sanity check on it first.

Reviewed-by Christoph Hellwig <hch at lst.de>
author maintainer
#12 lore raw

Re: [PATCH 3/7] nvme: implement mq_ops->commit_rqs() hook

Quoted 12 lines · Christoph Hellwig
Quoted 11 lines · Jens Axboe
Quoted 9 lines · Christoph Hellwig

Review

Quoted 7 lines
(quoted diff) +7 -0
+static inline int nvme_next_ring_index(struct nvme_queue *nvmeq, u16 index)
+{
+	if (++index == nvmeq->q_depth)
+		return 0;
+
+	return index;
+}

This is unused now.

Quoted 4 lines
Quoted 1 line

Huh, wonder how I missed that. GCC must not have complained.

gcc never warns about unused static inline functions. Which makes a lot of sense at least for headers..

Not so much for non-headers :-)

Quoted 6 lines
Quoted 4 lines
Quoted 1 line

Also what about this little cleanup on top?

That looks good, I like it. With that, can I add your reviewed-by? I'll run a sanity check on it first.

Reviewed-by Christoph Hellwig <hch at lst.de>

Thanks!

Signature · 1 line
Jens Axboe
#13 lore raw

Re: [PATCH 3/7] nvme: implement mq_ops->commit_rqs() hook

Quoted 5 lines · Jens Axboe
Quoted 2 lines · Christoph Hellwig

gcc never warns about unused static inline functions. Which makes a lot of sense at least for headers..

Not so much for non-headers :-)

You can #include .c files too! :)

author maintainer
#14 lore raw

Re: [PATCH 3/7] nvme: implement mq_ops->commit_rqs() hook

Quoted 8 lines · Keith Busch
Quoted 5 lines · Jens Axboe
Quoted 2 lines · Christoph Hellwig

gcc never warns about unused static inline functions. Which makes a lot of sense at least for headers..

Not so much for non-headers :-)

You can #include .c files too! :)

There's always that one guy...

Signature · 1 line
Jens Axboe
author maintainer
#15 lore raw

PATCH 4/7 virtio_blk: implement mq_ops->commit_rqs() hook

In reply to Jens Axboe

We need this for blk-mq to kick things into gear, if we told it that we had more IO coming, but then failed to deliver on that promise.

Reviewed-by Omar Sandoval <osandov at fb.com>
Acked-by Michael S. Tsirkin <mst at redhat.com>
Reviewed-by Christoph Hellwig <hch at lst.de>
Signed-off-by Jens Axboe <axboe at kernel.dk>
---
 drivers/block/virtio_blk.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
drivers/block/virtio_blk.c +15 -0
index 6e869d05f91e..912c4265e592 100644
@@ -214,6 +214,20 @@ static void virtblk_done(struct virtqueue *vq)
 	spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
 }
 
+static void virtio_commit_rqs(struct blk_mq_hw_ctx *hctx)
+{
+	struct virtio_blk *vblk = hctx->queue->queuedata;
+	struct virtio_blk_vq *vq = &vblk->vqs[hctx->queue_num];
+	bool kick;
+
+	spin_lock_irq(&vq->lock);
+	kick = virtqueue_kick_prepare(vq->vq);
+	spin_unlock_irq(&vq->lock);
+
+	if (kick)
+		virtqueue_notify(vq->vq);
+}
+
 static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
 			   const struct blk_mq_queue_data *bd)
 {

@@ -638,6 +652,7 @@ static void virtblk_initialize_rq(struct request *req)
 
 static const struct blk_mq_ops virtio_mq_ops = {
 	.queue_rq	= virtio_queue_rq,
+	.commit_rqs	= virtio_commit_rqs,
 	.complete	= virtblk_request_done,
 	.init_request	= virtblk_init_request,
 #ifdef CONFIG_VIRTIO_BLK_SCSI
Signature · 1 line
2.17.1
maintainer Reviewed-by on v1 4/7
#16 lore raw

Re: [PATCH 4/7] virtio_blk: implement mq_ops->commit_rqs() hook

Reviewed-by Sagi Grimberg <sagi at grimberg.me>
author maintainer
#17 lore raw

PATCH 5/7 ataflop: implement mq_ops->commit_rqs() hook

In reply to Jens Axboe

We need this for blk-mq to kick things into gear, if we told it that we had more IO coming, but then failed to deliver on that promise.

Reviewed-by Omar Sandoval <osandov at fb.com>
Signed-off-by Jens Axboe <axboe at kernel.dk>
---
 drivers/block/ataflop.c | 10 ++++++++++
 1 file changed, 10 insertions(+)
drivers/block/ataflop.c +10 -0
index f88b4c26d422..a0c6745b0034 100644
@@ -1471,6 +1471,15 @@ static void setup_req_params( int drive )
 			ReqTrack, ReqSector, (unsigned long)ReqData ));
 }
 
+static void ataflop_commit_rqs(struct blk_mq_hw_ctx *hctx)
+{
+	spin_lock_irq(&ataflop_lock);
+	atari_disable_irq(IRQ_MFP_FDC);
+	finish_fdc();
+	atari_enable_irq(IRQ_MFP_FDC);
+	spin_unlock_irq(&ataflop_lock);
+}
+
 static blk_status_t ataflop_queue_rq(struct blk_mq_hw_ctx *hctx,
 				     const struct blk_mq_queue_data *bd)
 {

@@ -1947,6 +1956,7 @@ static const struct block_device_operations floppy_fops = {
 
 static const struct blk_mq_ops ataflop_mq_ops = {
 	.queue_rq = ataflop_queue_rq,
+	.commit_rqs = ataflop_commit_rqs,
 };
 
 static struct kobject *floppy_find(dev_t dev, int *part, void *data)
Signature · 1 line
2.17.1
Reviewed-by on v1 5/7
#18 lore raw

Re: [PATCH 5/7] ataflop: implement mq_ops->commit_rqs() hook

Quoted 40 lines · Jens Axboe

We need this for blk-mq to kick things into gear, if we told it that we had more IO coming, but then failed to deliver on that promise.

Reviewed-by Omar Sandoval <osandov at fb.com>
Signed-off-by Jens Axboe <axboe at kernel.dk>
---
 drivers/block/ataflop.c | 10 ++++++++++
 1 file changed, 10 insertions(+)
drivers/block/ataflop.c +10 -0
index f88b4c26d422..a0c6745b0034 100644
@@ -1471,6 +1471,15 @@ static void setup_req_params( int drive )
 			ReqTrack, ReqSector, (unsigned long)ReqData ));
 }
 
+static void ataflop_commit_rqs(struct blk_mq_hw_ctx *hctx)
+{
+	spin_lock_irq(&ataflop_lock);
+	atari_disable_irq(IRQ_MFP_FDC);
+	finish_fdc();
+	atari_enable_irq(IRQ_MFP_FDC);
+	spin_unlock_irq(&ataflop_lock);
+}
+
 static blk_status_t ataflop_queue_rq(struct blk_mq_hw_ctx *hctx,
 				     const struct blk_mq_queue_data *bd)
 {

@@ -1947,6 +1956,7 @@ static const struct block_device_operations floppy_fops = {
 
 static const struct blk_mq_ops ataflop_mq_ops = {
 	.queue_rq = ataflop_queue_rq,
+	.commit_rqs = ataflop_commit_rqs,
 };
 
 static struct kobject *floppy_find(dev_t dev, int *part, void *data)
Signature · 1 line
2.17.1
Reviewed-by Ming Lei <ming.lei at redhat.com>

thanks,
Ming

Reviewed-by on v1 5/7
#19 lore raw

Re: [PATCH 5/7] ataflop: implement mq_ops->commit_rqs() hook

In reply to Jens Axboe
Quoted 5 lines · Jens Axboe

We need this for blk-mq to kick things into gear, if we told it that we had more IO coming, but then failed to deliver on that promise.

Reviewed-by Omar Sandoval <osandov at fb.com>
Signed-off-by Jens Axboe <axboe at kernel.dk>

Looks good,

Reviewed-by Christoph Hellwig <hch at lst.de>
author maintainer
#21 lore raw

PATCH 6/7 blk-mq: use bd->last == true for list inserts

In reply to Jens Axboe

If we are issuing a list of requests, we know if we're at the last one. If we fail issuing, ensure that we call ->commits_rqs() to flush any potential previous requests.

Reviewed-by Omar Sandoval <osandov at fb.com>
Signed-off-by Jens Axboe <axboe at kernel.dk>
---
 block/blk-core.c |  2 +-
 block/blk-mq.c   | 16 ++++++++--------
 block/blk-mq.h   |  2 +-
 3 files changed, 10 insertions(+), 10 deletions(-)
block/blk-core.c +1 -1
index d107d016b92b..3f6f5e6c2fe4 100644
@@ -1334,7 +1334,7 @@ blk_status_t blk_insert_cloned_request(struct request_queue *q, struct request *
 	 * bypass a potential scheduler on the bottom device for
 	 * insert.
 	 */
-	return blk_mq_request_issue_directly(rq);
+	return blk_mq_request_issue_directly(rq, true);
 }
 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
block/blk-mq.c +8 -8
index 18ff47a85ad3..9e1045152e45 100644
@@ -1743,12 +1743,12 @@ static blk_qc_t request_to_qc_t(struct blk_mq_hw_ctx *hctx, struct request *rq)
 
 static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
 					    struct request *rq,
-					    blk_qc_t *cookie)
+					    blk_qc_t *cookie, bool last)
 {
 	struct request_queue *q = rq->q;
 	struct blk_mq_queue_data bd = {
 		.rq = rq,
-		.last = true,
+		.last = last,
 	};
 	blk_qc_t new_cookie;
 	blk_status_t ret;

@@ -1783,7 +1783,7 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
 static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 						struct request *rq,
 						blk_qc_t *cookie,
-						bool bypass_insert)
+						bool bypass_insert, bool last)
 {
 	struct request_queue *q = rq->q;
 	bool run_queue = true;

@@ -1812,7 +1812,7 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 		goto insert;
 	}
 
-	return __blk_mq_issue_directly(hctx, rq, cookie);
+	return __blk_mq_issue_directly(hctx, rq, cookie, last);
 insert:
 	if (bypass_insert)
 		return BLK_STS_RESOURCE;

@@ -1831,7 +1831,7 @@ static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 
 	hctx_lock(hctx, &srcu_idx);
 
-	ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false);
+	ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false, true);
 	if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
 		blk_mq_sched_insert_request(rq, false, true, false);
 	else if (ret != BLK_STS_OK)

@@ -1840,7 +1840,7 @@ static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 	hctx_unlock(hctx, srcu_idx);
 }
 
-blk_status_t blk_mq_request_issue_directly(struct request *rq)
+blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last)
 {
 	blk_status_t ret;
 	int srcu_idx;

@@ -1848,7 +1848,7 @@ blk_status_t blk_mq_request_issue_directly(struct request *rq)
 	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
 
 	hctx_lock(hctx, &srcu_idx);
-	ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true);
+	ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true, last);
 	hctx_unlock(hctx, srcu_idx);
 
 	return ret;

@@ -1863,7 +1863,7 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
 				queuelist);
 
 		list_del_init(&rq->queuelist);
-		ret = blk_mq_request_issue_directly(rq);
+		ret = blk_mq_request_issue_directly(rq, list_empty(list));
 		if (ret != BLK_STS_OK) {
 			if (ret == BLK_STS_RESOURCE ||
 					ret == BLK_STS_DEV_RESOURCE) {
block/blk-mq.h +1 -1
index 9ae8e9f8f8b1..7291e5379358 100644
@@ -69,7 +69,7 @@ void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
 				struct list_head *list);
 
 /* Used by blk_insert_cloned_request() to issue request directly */
-blk_status_t blk_mq_request_issue_directly(struct request *rq);
+blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last);
 void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
 				    struct list_head *list);
Signature · 1 line
2.17.1
Reviewed-by on v1 6/7
#22 lore raw

Re: [PATCH 6/7] blk-mq: use bd->last == true for list inserts

Quoted 114 lines · Jens Axboe

If we are issuing a list of requests, we know if we're at the last one. If we fail issuing, ensure that we call ->commits_rqs() to flush any potential previous requests.

Reviewed-by Omar Sandoval <osandov at fb.com>
Signed-off-by Jens Axboe <axboe at kernel.dk>
---
 block/blk-core.c |  2 +-
 block/blk-mq.c   | 16 ++++++++--------
 block/blk-mq.h   |  2 +-
 3 files changed, 10 insertions(+), 10 deletions(-)
block/blk-core.c +1 -1
index d107d016b92b..3f6f5e6c2fe4 100644
@@ -1334,7 +1334,7 @@ blk_status_t blk_insert_cloned_request(struct request_queue *q, struct request *
 	 * bypass a potential scheduler on the bottom device for
 	 * insert.
 	 */
-	return blk_mq_request_issue_directly(rq);
+	return blk_mq_request_issue_directly(rq, true);
 }
 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
block/blk-mq.c +8 -8
index 18ff47a85ad3..9e1045152e45 100644
@@ -1743,12 +1743,12 @@ static blk_qc_t request_to_qc_t(struct blk_mq_hw_ctx *hctx, struct request *rq)
 
 static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
 					    struct request *rq,
-					    blk_qc_t *cookie)
+					    blk_qc_t *cookie, bool last)
 {
 	struct request_queue *q = rq->q;
 	struct blk_mq_queue_data bd = {
 		.rq = rq,
-		.last = true,
+		.last = last,
 	};
 	blk_qc_t new_cookie;
 	blk_status_t ret;

@@ -1783,7 +1783,7 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
 static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 						struct request *rq,
 						blk_qc_t *cookie,
-						bool bypass_insert)
+						bool bypass_insert, bool last)
 {
 	struct request_queue *q = rq->q;
 	bool run_queue = true;

@@ -1812,7 +1812,7 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 		goto insert;
 	}
 
-	return __blk_mq_issue_directly(hctx, rq, cookie);
+	return __blk_mq_issue_directly(hctx, rq, cookie, last);
 insert:
 	if (bypass_insert)
 		return BLK_STS_RESOURCE;

@@ -1831,7 +1831,7 @@ static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 
 	hctx_lock(hctx, &srcu_idx);
 
-	ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false);
+	ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false, true);
 	if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
 		blk_mq_sched_insert_request(rq, false, true, false);
 	else if (ret != BLK_STS_OK)

@@ -1840,7 +1840,7 @@ static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 	hctx_unlock(hctx, srcu_idx);
 }
 
-blk_status_t blk_mq_request_issue_directly(struct request *rq)
+blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last)
 {
 	blk_status_t ret;
 	int srcu_idx;

@@ -1848,7 +1848,7 @@ blk_status_t blk_mq_request_issue_directly(struct request *rq)
 	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
 
 	hctx_lock(hctx, &srcu_idx);
-	ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true);
+	ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true, last);
 	hctx_unlock(hctx, srcu_idx);
 
 	return ret;

@@ -1863,7 +1863,7 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
 				queuelist);
 
 		list_del_init(&rq->queuelist);
-		ret = blk_mq_request_issue_directly(rq);
+		ret = blk_mq_request_issue_directly(rq, list_empty(list));
 		if (ret != BLK_STS_OK) {
 			if (ret == BLK_STS_RESOURCE ||
 					ret == BLK_STS_DEV_RESOURCE) {
block/blk-mq.h +1 -1
index 9ae8e9f8f8b1..7291e5379358 100644
@@ -69,7 +69,7 @@ void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
 				struct list_head *list);
 
 /* Used by blk_insert_cloned_request() to issue request directly */
-blk_status_t blk_mq_request_issue_directly(struct request *rq);
+blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last);
 void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
 				    struct list_head *list);
Signature · 1 line
2.17.1
Reviewed-by Ming Lei <ming.lei at redhat.com>

Thanks,
Ming

Reviewed-by on v1 6/7
#23 lore raw

Re: [PATCH 6/7] blk-mq: use bd->last == true for list inserts

In reply to Jens Axboe
Quoted 6 lines · Jens Axboe

If we are issuing a list of requests, we know if we're at the last one. If we fail issuing, ensure that we call ->commits_rqs() to flush any potential previous requests.

Reviewed-by Omar Sandoval <osandov at fb.com>
Signed-off-by Jens Axboe <axboe at kernel.dk>

Looks good,

Reviewed-by Christoph Hellwig <hch at lst.de>
author maintainer
#25 lore raw

PATCH 7/7 blk-mq: use plug for devices that implement ->commits_rqs()

In reply to Jens Axboe

If we have that hook, we know the driver handles bd->last == true in a smart fashion. If it does, even for multiple hardware queues, it's a good idea to flush batches of requests to the device, if we have batches of requests from the submitter.

Signed-off-by Jens Axboe <axboe at kernel.dk>
---
 block/blk-mq.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
block/blk-mq.c +6 -1
index 9e1045152e45..091557a43d53 100644
@@ -1945,7 +1945,12 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 		/* bypass scheduler for flush rq */
 		blk_insert_flush(rq);
 		blk_mq_run_hw_queue(data.hctx, true);
-	} else if (plug && q->nr_hw_queues == 1) {
+	} else if (plug && (q->nr_hw_queues == 1 || q->mq_ops->commit_rqs)) {
+		/*
+		 * Use plugging if we have a ->commit_rqs() hook as well,
+		 * as we know the driver uses bd->last in a smart
+		 * fashion.
+		 */
 		unsigned int request_count = plug->rq_count;
 		struct request *last = NULL;
Signature · 1 line
2.17.1
Reviewed-by on v1 7/7
#26 lore raw

Re: [PATCH 7/7] blk-mq: use plug for devices that implement ->commits_rqs()

Quoted 31 lines · Jens Axboe

If we have that hook, we know the driver handles bd->last == true in a smart fashion. If it does, even for multiple hardware queues, it's a good idea to flush batches of requests to the device, if we have batches of requests from the submitter.

Signed-off-by Jens Axboe <axboe at kernel.dk>
---
 block/blk-mq.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
block/blk-mq.c +6 -1
index 9e1045152e45..091557a43d53 100644
@@ -1945,7 +1945,12 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 		/* bypass scheduler for flush rq */
 		blk_insert_flush(rq);
 		blk_mq_run_hw_queue(data.hctx, true);
-	} else if (plug && q->nr_hw_queues == 1) {
+	} else if (plug && (q->nr_hw_queues == 1 || q->mq_ops->commit_rqs)) {
+		/*
+		 * Use plugging if we have a ->commit_rqs() hook as well,
+		 * as we know the driver uses bd->last in a smart
+		 * fashion.
+		 */
 		unsigned int request_count = plug->rq_count;
 		struct request *last = NULL;
Signature · 1 line
2.17.1
Reviewed-by Ming Lei <ming.lei at redhat.com>

thanks,
Ming

#27 lore raw

Re: [PATCH 7/7] blk-mq: use plug for devices that implement ->commits_rqs()

In reply to Jens Axboe

block/blk-mq.c static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) · line 1953

Quoted 5 lines
block/blk-mq.c +5 -0
+		/*
+		 * Use plugging if we have a ->commit_rqs() hook as well,
+		 * as we know the driver uses bd->last in a smart
+		 * fashion.
+		 */

Nipick: this could flow on just two lines:

		/*
		 * Use plugging if we have a ->commit_rqs() hook as well, as we
		 * know the driver uses bd->last in a smart fashion.
		 */
Reviewed-by
#28 lore raw

Re: [PATCH 7/7] blk-mq: use plug for devices that implement ->commits_rqs()

Quoted 8 lines · Christoph Hellwig

block/blk-mq.c static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) · line 1953

Quoted 5 lines
block/blk-mq.c +5 -0
+		/*
+		 * Use plugging if we have a ->commit_rqs() hook as well,
+		 * as we know the driver uses bd->last in a smart
+		 * fashion.
+		 */

Nipick: this could flow on just two lines:

Quoted 4 lines
		/*
		 * Use plugging if we have a ->commit_rqs() hook as well, as we
		 * know the driver uses bd->last in a smart fashion.
		 */

But of course otherwise this looks fine:

Reviewed-by Christoph Hellwig <hch at lst.de>
author maintainer
#29 lore raw

Re: [PATCH 7/7] blk-mq: use plug for devices that implement ->commits_rqs()

In reply to Christoph Hellwig
Quoted 8 lines · Christoph Hellwig

block/blk-mq.c static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) · line 1953

Quoted 5 lines
block/blk-mq.c +5 -0
+		/*
+		 * Use plugging if we have a ->commit_rqs() hook as well,
+		 * as we know the driver uses bd->last in a smart
+		 * fashion.
+		 */

Nipick: this could flow on just two lines:

Quoted 4 lines
		/*
		 * Use plugging if we have a ->commit_rqs() hook as well, as we
		 * know the driver uses bd->last in a smart fashion.
		 */

Fixed up.

Signature · 1 line
Jens Axboe
maintainer Reviewed-by on v1 7/7
#30 lore raw

Re: [PATCH 7/7] blk-mq: use plug for devices that implement ->commits_rqs()

In reply to Jens Axboe
Reviewed-by Sagi Grimberg <sagi at grimberg.me>