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linux-next/block/blk-mq-tag.h
Jens Axboe 59d13bf5f5 blk-mq: use sparser tag layout for lower queue depth
For best performance, spreading tags over multiple cachelines
makes the tagging more efficient on multicore systems. But since
we have 8 * sizeof(unsigned long) tags per cacheline, we don't
always get a nice spread.

Attempt to spread the tags over at least 4 cachelines, using fewer
number of bits per unsigned long if we have to. This improves
tagging performance in setups with 32-128 tags. For higher depths,
the spread is the same as before (BITS_PER_LONG tags per cacheline).

Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-09 13:41:15 -06:00

72 lines
1.9 KiB
C

#ifndef INT_BLK_MQ_TAG_H
#define INT_BLK_MQ_TAG_H
enum {
BT_WAIT_QUEUES = 8,
BT_WAIT_BATCH = 8,
};
struct bt_wait_state {
atomic_t wait_cnt;
wait_queue_head_t wait;
} ____cacheline_aligned_in_smp;
#define TAG_TO_INDEX(bt, tag) ((tag) >> (bt)->bits_per_word)
#define TAG_TO_BIT(bt, tag) ((tag) & ((1 << (bt)->bits_per_word) - 1))
struct blk_mq_bitmap {
unsigned long word;
unsigned long depth;
} ____cacheline_aligned_in_smp;
struct blk_mq_bitmap_tags {
unsigned int depth;
unsigned int wake_cnt;
unsigned int bits_per_word;
unsigned int map_nr;
struct blk_mq_bitmap *map;
unsigned int wake_index;
struct bt_wait_state *bs;
};
/*
* Tag address space map.
*/
struct blk_mq_tags {
unsigned int nr_tags;
unsigned int nr_reserved_tags;
struct blk_mq_bitmap_tags bitmap_tags;
struct blk_mq_bitmap_tags breserved_tags;
struct request **rqs;
struct list_head page_list;
};
extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node);
extern void blk_mq_free_tags(struct blk_mq_tags *tags);
extern unsigned int blk_mq_get_tag(struct blk_mq_tags *tags, struct blk_mq_hw_ctx *hctx, unsigned int *last_tag, gfp_t gfp, bool reserved);
extern void blk_mq_wait_for_tags(struct blk_mq_tags *tags, struct blk_mq_hw_ctx *hctx, bool reserved);
extern void blk_mq_put_tag(struct blk_mq_tags *tags, unsigned int tag, unsigned int *last_tag);
extern void blk_mq_tag_busy_iter(struct blk_mq_tags *tags, void (*fn)(void *data, unsigned long *), void *data);
extern bool blk_mq_has_free_tags(struct blk_mq_tags *tags);
extern ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page);
extern void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *last_tag);
enum {
BLK_MQ_TAG_CACHE_MIN = 1,
BLK_MQ_TAG_CACHE_MAX = 64,
};
enum {
BLK_MQ_TAG_FAIL = -1U,
BLK_MQ_TAG_MIN = BLK_MQ_TAG_CACHE_MIN,
BLK_MQ_TAG_MAX = BLK_MQ_TAG_FAIL - 1,
};
#endif