From ee1b6f7aff94019c09e73837054979063f722046 Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Thu, 15 Jan 2015 17:32:25 -0800 Subject: 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 Cc: Tejun Heo Cc: Christoph Hellwig Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe --- block/blk-tag.c | 33 +++++++++++++++++++++++++-------- 1 file changed, 25 insertions(+), 8 deletions(-) (limited to 'block') diff --git a/block/blk-tag.c b/block/blk-tag.c index a185b86741e5..f0344e6939d5 100644 --- a/block/blk-tag.c +++ b/block/blk-tag.c @@ -119,7 +119,7 @@ fail: } 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 @@ fail: /** * 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; -- cgit v1.2.3