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: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Shaohua Li
Jens Axboe
parent
ee1b6f7aff
commit
24391c0dc5
5 changed files with 39 additions and 17 deletions
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@ -140,7 +140,8 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
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return atomic_read(&hctx->nr_active) < depth;
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}
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static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
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static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag,
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bool nowrap)
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{
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int tag, org_last_tag = last_tag;
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@ -152,7 +153,7 @@ static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
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* offset to 0 in a failure case, so start from 0 to
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* exhaust the map.
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*/
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if (org_last_tag && last_tag) {
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if (org_last_tag && last_tag && !nowrap) {
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last_tag = org_last_tag = 0;
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continue;
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}
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@ -170,6 +171,8 @@ static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
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return tag;
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}
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#define BT_ALLOC_RR(tags) (tags->alloc_policy == BLK_TAG_ALLOC_RR)
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/*
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* Straight forward bitmap tag implementation, where each bit is a tag
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* (cleared == free, and set == busy). The small twist is using per-cpu
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@ -182,7 +185,7 @@ static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
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* until the map is exhausted.
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*/
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static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,
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unsigned int *tag_cache)
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unsigned int *tag_cache, struct blk_mq_tags *tags)
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{
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unsigned int last_tag, org_last_tag;
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int index, i, tag;
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@ -194,7 +197,8 @@ static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,
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index = TAG_TO_INDEX(bt, last_tag);
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for (i = 0; i < bt->map_nr; i++) {
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tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag));
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tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag),
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BT_ALLOC_RR(tags));
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if (tag != -1) {
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tag += (index << bt->bits_per_word);
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goto done;
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@ -221,7 +225,7 @@ static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,
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* up using the specific cached tag.
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*/
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done:
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if (tag == org_last_tag) {
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if (tag == org_last_tag || unlikely(BT_ALLOC_RR(tags))) {
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last_tag = tag + 1;
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if (last_tag >= bt->depth - 1)
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last_tag = 0;
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@ -250,13 +254,13 @@ static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt,
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static int bt_get(struct blk_mq_alloc_data *data,
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struct blk_mq_bitmap_tags *bt,
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struct blk_mq_hw_ctx *hctx,
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unsigned int *last_tag)
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unsigned int *last_tag, struct blk_mq_tags *tags)
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{
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struct bt_wait_state *bs;
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DEFINE_WAIT(wait);
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int tag;
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tag = __bt_get(hctx, bt, last_tag);
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tag = __bt_get(hctx, bt, last_tag, tags);
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if (tag != -1)
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return tag;
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@ -267,7 +271,7 @@ static int bt_get(struct blk_mq_alloc_data *data,
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do {
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prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE);
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tag = __bt_get(hctx, bt, last_tag);
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tag = __bt_get(hctx, bt, last_tag, tags);
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if (tag != -1)
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break;
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@ -282,7 +286,7 @@ static int bt_get(struct blk_mq_alloc_data *data,
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* Retry tag allocation after running the hardware queue,
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* as running the queue may also have found completions.
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*/
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tag = __bt_get(hctx, bt, last_tag);
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tag = __bt_get(hctx, bt, last_tag, tags);
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if (tag != -1)
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break;
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@ -313,7 +317,7 @@ static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data)
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int tag;
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tag = bt_get(data, &data->hctx->tags->bitmap_tags, data->hctx,
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&data->ctx->last_tag);
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&data->ctx->last_tag, data->hctx->tags);
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if (tag >= 0)
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return tag + data->hctx->tags->nr_reserved_tags;
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@ -329,7 +333,8 @@ static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_alloc_data *data)
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return BLK_MQ_TAG_FAIL;
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}
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tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, &zero);
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tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, &zero,
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data->hctx->tags);
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if (tag < 0)
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return BLK_MQ_TAG_FAIL;
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@ -401,7 +406,8 @@ void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag,
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BUG_ON(real_tag >= tags->nr_tags);
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bt_clear_tag(&tags->bitmap_tags, real_tag);
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*last_tag = real_tag;
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if (likely(tags->alloc_policy == BLK_TAG_ALLOC_FIFO))
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*last_tag = real_tag;
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} else {
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BUG_ON(tag >= tags->nr_reserved_tags);
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bt_clear_tag(&tags->breserved_tags, tag);
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@ -538,10 +544,12 @@ static void bt_free(struct blk_mq_bitmap_tags *bt)
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}
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static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
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int node)
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int node, int alloc_policy)
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{
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unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
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tags->alloc_policy = alloc_policy;
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if (bt_alloc(&tags->bitmap_tags, depth, node, false))
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goto enomem;
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if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node, true))
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@ -555,7 +563,8 @@ static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
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}
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struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
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unsigned int reserved_tags, int node)
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unsigned int reserved_tags,
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int node, int alloc_policy)
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{
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struct blk_mq_tags *tags;
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@ -571,7 +580,7 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
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tags->nr_tags = total_tags;
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tags->nr_reserved_tags = reserved_tags;
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return blk_mq_init_bitmap_tags(tags, node);
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return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
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}
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void blk_mq_free_tags(struct blk_mq_tags *tags)
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@ -42,10 +42,12 @@ struct blk_mq_tags {
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struct request **rqs;
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struct list_head page_list;
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int alloc_policy;
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};
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extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node);
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extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node, int alloc_policy);
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extern void blk_mq_free_tags(struct blk_mq_tags *tags);
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extern unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data);
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@ -1374,7 +1374,8 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
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size_t rq_size, left;
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tags = blk_mq_init_tags(set->queue_depth, set->reserved_tags,
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set->numa_node);
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set->numa_node,
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BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
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if (!tags)
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return NULL;
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@ -2188,6 +2188,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
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shost->tag_set.cmd_size = cmd_size;
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shost->tag_set.numa_node = NUMA_NO_NODE;
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shost->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE;
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shost->tag_set.flags |=
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BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
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shost->tag_set.driver_data = shost;
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return blk_mq_alloc_tag_set(&shost->tag_set);
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@ -147,6 +147,8 @@ enum {
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BLK_MQ_F_SG_MERGE = 1 << 2,
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BLK_MQ_F_SYSFS_UP = 1 << 3,
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BLK_MQ_F_DEFER_ISSUE = 1 << 4,
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BLK_MQ_F_ALLOC_POLICY_START_BIT = 8,
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BLK_MQ_F_ALLOC_POLICY_BITS = 1,
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BLK_MQ_S_STOPPED = 0,
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BLK_MQ_S_TAG_ACTIVE = 1,
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@ -155,6 +157,12 @@ enum {
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BLK_MQ_CPU_WORK_BATCH = 8,
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};
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#define BLK_MQ_FLAG_TO_ALLOC_POLICY(flags) \
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((flags >> BLK_MQ_F_ALLOC_POLICY_START_BIT) & \
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((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1))
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#define BLK_ALLOC_POLICY_TO_MQ_FLAG(policy) \
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((policy & ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1)) \
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<< BLK_MQ_F_ALLOC_POLICY_START_BIT)
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struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *);
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void blk_mq_finish_init(struct request_queue *q);
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