block: support different tag allocation policy

The libata tag allocation is using a round-robin policy. Next patch will
make libata use block generic tag allocation, so let's add a policy to
tag allocation.

Currently two policies: FIFO (default) and round-robin.

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 2015-01-15 17:32:25 -08:00 committed by Jens Axboe
parent bb5c3cdda3
commit ee1b6f7aff
6 changed files with 39 additions and 13 deletions

View File

@ -119,7 +119,7 @@ init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
}
static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
int depth)
int depth, int alloc_policy)
{
struct blk_queue_tag *tags;
@ -131,6 +131,8 @@ static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
goto fail;
atomic_set(&tags->refcnt, 1);
tags->alloc_policy = alloc_policy;
tags->next_tag = 0;
return tags;
fail:
kfree(tags);
@ -140,10 +142,11 @@ static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
/**
* blk_init_tags - initialize the tag info for an external tag map
* @depth: the maximum queue depth supported
* @alloc_policy: tag allocation policy
**/
struct blk_queue_tag *blk_init_tags(int depth)
struct blk_queue_tag *blk_init_tags(int depth, int alloc_policy)
{
return __blk_queue_init_tags(NULL, depth);
return __blk_queue_init_tags(NULL, depth, alloc_policy);
}
EXPORT_SYMBOL(blk_init_tags);
@ -152,19 +155,20 @@ EXPORT_SYMBOL(blk_init_tags);
* @q: the request queue for the device
* @depth: the maximum queue depth supported
* @tags: the tag to use
* @alloc_policy: tag allocation policy
*
* Queue lock must be held here if the function is called to resize an
* existing map.
**/
int blk_queue_init_tags(struct request_queue *q, int depth,
struct blk_queue_tag *tags)
struct blk_queue_tag *tags, int alloc_policy)
{
int rc;
BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
if (!tags && !q->queue_tags) {
tags = __blk_queue_init_tags(q, depth);
tags = __blk_queue_init_tags(q, depth, alloc_policy);
if (!tags)
return -ENOMEM;
@ -344,9 +348,21 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq)
}
do {
tag = find_first_zero_bit(bqt->tag_map, max_depth);
if (tag >= max_depth)
return 1;
if (bqt->alloc_policy == BLK_TAG_ALLOC_FIFO) {
tag = find_first_zero_bit(bqt->tag_map, max_depth);
if (tag >= max_depth)
return 1;
} else {
int start = bqt->next_tag;
int size = min_t(int, bqt->max_depth, max_depth + start);
tag = find_next_zero_bit(bqt->tag_map, size, start);
if (tag >= size && start + size > bqt->max_depth) {
size = start + size - bqt->max_depth;
tag = find_first_zero_bit(bqt->tag_map, size);
}
if (tag >= size)
return 1;
}
} while (test_and_set_bit_lock(tag, bqt->tag_map));
/*
@ -354,6 +370,7 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq)
* See blk_queue_end_tag for details.
*/
bqt->next_tag = (tag + 1) % bqt->max_depth;
rq->cmd_flags |= REQ_QUEUED;
rq->tag = tag;
bqt->tag_index[tag] = rq;

View File

@ -423,7 +423,7 @@ static int osdblk_init_disk(struct osdblk_device *osdev)
}
/* switch queue to TCQ mode; allocate tag map */
rc = blk_queue_init_tags(q, OSDBLK_MAX_REQ, NULL);
rc = blk_queue_init_tags(q, OSDBLK_MAX_REQ, NULL, BLK_TAG_ALLOC_FIFO);
if (rc) {
blk_cleanup_queue(q);
put_disk(disk);

View File

@ -290,7 +290,8 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
if (!shost_use_blk_mq(sdev->host) &&
(shost->bqt || shost->hostt->use_blk_tags)) {
blk_queue_init_tags(sdev->request_queue,
sdev->host->cmd_per_lun, shost->bqt);
sdev->host->cmd_per_lun, shost->bqt,
shost->hostt->tag_alloc_policy);
}
scsi_change_queue_depth(sdev, sdev->host->cmd_per_lun);

View File

@ -272,7 +272,11 @@ struct blk_queue_tag {
int max_depth; /* what we will send to device */
int real_max_depth; /* what the array can hold */
atomic_t refcnt; /* map can be shared */
int alloc_policy; /* tag allocation policy */
int next_tag; /* next tag */
};
#define BLK_TAG_ALLOC_FIFO 0 /* allocate starting from 0 */
#define BLK_TAG_ALLOC_RR 1 /* allocate starting from last allocated tag */
#define BLK_SCSI_MAX_CMDS (256)
#define BLK_SCSI_CMD_PER_LONG (BLK_SCSI_MAX_CMDS / (sizeof(long) * 8))
@ -1139,11 +1143,11 @@ static inline bool blk_needs_flush_plug(struct task_struct *tsk)
extern int blk_queue_start_tag(struct request_queue *, struct request *);
extern struct request *blk_queue_find_tag(struct request_queue *, int);
extern void blk_queue_end_tag(struct request_queue *, struct request *);
extern int blk_queue_init_tags(struct request_queue *, int, struct blk_queue_tag *);
extern int blk_queue_init_tags(struct request_queue *, int, struct blk_queue_tag *, int);
extern void blk_queue_free_tags(struct request_queue *);
extern int blk_queue_resize_tags(struct request_queue *, int);
extern void blk_queue_invalidate_tags(struct request_queue *);
extern struct blk_queue_tag *blk_init_tags(int);
extern struct blk_queue_tag *blk_init_tags(int, int);
extern void blk_free_tags(struct blk_queue_tag *);
static inline struct request *blk_map_queue_find_tag(struct blk_queue_tag *bqt,

View File

@ -402,6 +402,9 @@ struct scsi_host_template {
*/
unsigned char present;
/* If use block layer to manage tags, this is tag allocation policy */
int tag_alloc_policy;
/*
* Let the block layer assigns tags to all commands.
*/

View File

@ -66,7 +66,8 @@ static inline int scsi_init_shared_tag_map(struct Scsi_Host *shost, int depth)
* devices on the shared host (for libata)
*/
if (!shost->bqt) {
shost->bqt = blk_init_tags(depth);
shost->bqt = blk_init_tags(depth,
shost->hostt->tag_alloc_policy);
if (!shost->bqt)
return -ENOMEM;
}