Commit 24391c0d authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
Browse files

blk-mq: add tag allocation policy 



This is the blk-mq part to support tag allocation policy. The default
allocation policy isn't changed (though it's not a strict FIFO). The new
policy is round-robin for libata. But it's a try-best implementation. If
multiple tasks are competing, the tags returned will be mixed (which is
unavoidable even with !mq, as requests from different tasks can be
mixed in queue)

Cc: Jens Axboe <axboe@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent ee1b6f7a

block/blk-mq-tag.c

+24 −15
Original line number Diff line number Diff line
@@ -140,7 +140,8 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx, 
	return atomic_read(&hctx->nr_active) < depth;

}



static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)

static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag,

			 bool nowrap)

{

	int tag, org_last_tag = last_tag;
@@ -152,7 +153,7 @@ static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag) 
			 * offset to 0 in a failure case, so start from 0 to

			 * exhaust the map.

			 */

			if (org_last_tag && last_tag) {

			if (org_last_tag && last_tag && !nowrap) {

				last_tag = org_last_tag = 0;

				continue;

			}
@@ -170,6 +171,8 @@ static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag) 
	return tag;

}



#define BT_ALLOC_RR(tags) (tags->alloc_policy == BLK_TAG_ALLOC_RR)



/*

 * Straight forward bitmap tag implementation, where each bit is a tag

 * (cleared == free, and set == busy). The small twist is using per-cpu
@@ -182,7 +185,7 @@ static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag) 
 * until the map is exhausted.

 */

static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,

		    unsigned int *tag_cache)

		    unsigned int *tag_cache, struct blk_mq_tags *tags)

{

	unsigned int last_tag, org_last_tag;

	int index, i, tag;
@@ -194,7 +197,8 @@ static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt, 
	index = TAG_TO_INDEX(bt, last_tag);



	for (i = 0; i < bt->map_nr; i++) {

		tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag));

		tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag),

				    BT_ALLOC_RR(tags));

		if (tag != -1) {

			tag += (index << bt->bits_per_word);

			goto done;
@@ -221,7 +225,7 @@ static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt, 
	 * up using the specific cached tag.

	 */

done:

	if (tag == org_last_tag) {

	if (tag == org_last_tag || unlikely(BT_ALLOC_RR(tags))) {

		last_tag = tag + 1;

		if (last_tag >= bt->depth - 1)

			last_tag = 0;
@@ -250,13 +254,13 @@ static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt, 
static int bt_get(struct blk_mq_alloc_data *data,

		struct blk_mq_bitmap_tags *bt,

		struct blk_mq_hw_ctx *hctx,

		unsigned int *last_tag)

		unsigned int *last_tag, struct blk_mq_tags *tags)

{

	struct bt_wait_state *bs;

	DEFINE_WAIT(wait);

	int tag;



	tag = __bt_get(hctx, bt, last_tag);

	tag = __bt_get(hctx, bt, last_tag, tags);

	if (tag != -1)

		return tag;
@@ -267,7 +271,7 @@ static int bt_get(struct blk_mq_alloc_data *data, 
	do {

		prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE);



		tag = __bt_get(hctx, bt, last_tag);

		tag = __bt_get(hctx, bt, last_tag, tags);

		if (tag != -1)

			break;
@@ -282,7 +286,7 @@ static int bt_get(struct blk_mq_alloc_data *data, 
		 * Retry tag allocation after running the hardware queue,

		 * as running the queue may also have found completions.

		 */

		tag = __bt_get(hctx, bt, last_tag);

		tag = __bt_get(hctx, bt, last_tag, tags);

		if (tag != -1)

			break;
@@ -313,7 +317,7 @@ static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data) 
	int tag;



	tag = bt_get(data, &data->hctx->tags->bitmap_tags, data->hctx,

			&data->ctx->last_tag);

			&data->ctx->last_tag, data->hctx->tags);

	if (tag >= 0)

		return tag + data->hctx->tags->nr_reserved_tags;
@@ -329,7 +333,8 @@ static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_alloc_data *data) 
		return BLK_MQ_TAG_FAIL;

	}



	tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, &zero);

	tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, &zero,

		data->hctx->tags);

	if (tag < 0)

		return BLK_MQ_TAG_FAIL;
@@ -401,6 +406,7 @@ void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag, 


		BUG_ON(real_tag >= tags->nr_tags);

		bt_clear_tag(&tags->bitmap_tags, real_tag);

		if (likely(tags->alloc_policy == BLK_TAG_ALLOC_FIFO))

			*last_tag = real_tag;

	} else {

		BUG_ON(tag >= tags->nr_reserved_tags);
@@ -538,10 +544,12 @@ static void bt_free(struct blk_mq_bitmap_tags *bt) 
}



static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,

						   int node)

						   int node, int alloc_policy)

{

	unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;



	tags->alloc_policy = alloc_policy;



	if (bt_alloc(&tags->bitmap_tags, depth, node, false))

		goto enomem;

	if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node, true))
@@ -555,7 +563,8 @@ enomem: 
}



struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,

				     unsigned int reserved_tags, int node)

				     unsigned int reserved_tags,

				     int node, int alloc_policy)

{

	struct blk_mq_tags *tags;
@@ -571,7 +580,7 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, 
	tags->nr_tags = total_tags;

	tags->nr_reserved_tags = reserved_tags;



	return blk_mq_init_bitmap_tags(tags, node);

	return blk_mq_init_bitmap_tags(tags, node, alloc_policy);

}



void blk_mq_free_tags(struct blk_mq_tags *tags)

block/blk-mq-tag.h

+3 −1
Original line number Diff line number Diff line
@@ -42,10 +42,12 @@ struct blk_mq_tags { 


	struct request **rqs;

	struct list_head page_list;



	int alloc_policy;

};





extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node);

extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node, int alloc_policy);

extern void blk_mq_free_tags(struct blk_mq_tags *tags);



extern unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data);

block/blk-mq.c

+2 −1
Original line number Diff line number Diff line
@@ -1374,7 +1374,8 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set, 
	size_t rq_size, left;



	tags = blk_mq_init_tags(set->queue_depth, set->reserved_tags,

				set->numa_node);

				set->numa_node,

				BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));

	if (!tags)

		return NULL;

drivers/scsi/scsi_lib.c

+2 −0
Original line number Diff line number Diff line
@@ -2188,6 +2188,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) 
	shost->tag_set.cmd_size = cmd_size;

	shost->tag_set.numa_node = NUMA_NO_NODE;

	shost->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE;

	shost->tag_set.flags |=

		BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);

	shost->tag_set.driver_data = shost;



	return blk_mq_alloc_tag_set(&shost->tag_set);

include/linux/blk-mq.h

+8 −0
Original line number Diff line number Diff line
@@ -147,6 +147,8 @@ enum { 
	BLK_MQ_F_SG_MERGE	= 1 << 2,

	BLK_MQ_F_SYSFS_UP	= 1 << 3,

	BLK_MQ_F_DEFER_ISSUE	= 1 << 4,

	BLK_MQ_F_ALLOC_POLICY_START_BIT = 8,

	BLK_MQ_F_ALLOC_POLICY_BITS = 1,



	BLK_MQ_S_STOPPED	= 0,

	BLK_MQ_S_TAG_ACTIVE	= 1,
@@ -155,6 +157,12 @@ enum { 


	BLK_MQ_CPU_WORK_BATCH	= 8,

};

#define BLK_MQ_FLAG_TO_ALLOC_POLICY(flags) \

	((flags >> BLK_MQ_F_ALLOC_POLICY_START_BIT) & \

		((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1))

#define BLK_ALLOC_POLICY_TO_MQ_FLAG(policy) \

	((policy & ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1)) \

		<< BLK_MQ_F_ALLOC_POLICY_START_BIT)



struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *);

void blk_mq_finish_init(struct request_queue *q);

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