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blk-mq: add tag allocation policy

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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: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Shaohua Li 2015-01-23 14:18:00 -07:00 committed by Jens Axboe
parent ee1b6f7aff
commit 24391c0dc5
5 changed files with 39 additions and 17 deletions
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39
block/blk-mq-tag.c
View File

@ -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;
@ -401,7 +406,8 @@ 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);
*last_tag = real_tag;
if (likely(tags->alloc_policy == BLK_TAG_ALLOC_FIFO))
*last_tag = real_tag;
} else {
BUG_ON(tag >= tags->nr_reserved_tags);
bt_clear_tag(&tags->breserved_tags, tag);
@ -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)

4
block/blk-mq-tag.h
View File

@ -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);

3
block/blk-mq.c
View File

@ -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;

2
drivers/scsi/scsi_lib.c
View File

@ -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);

8
include/linux/blk-mq.h
View File

@ -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);