[PATCH 2/4] block: inline fast path of driver tag allocation

Jens Axboe
2021-10-13T16:49:44Z

If we don't use an IO scheduler or have shared tags, then we don't need
to call into this external function at all. This saves ~2% for such
a setup.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
block/blk-mq.c | 8 +++-----
block/blk-mq.h | 15 ++++++++++++++-
2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 46a91e5fabc5..fe3e926c20a9 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1135,7 +1135,7 @@ static inline unsigned int queued_to_index(unsigned int queued)
return min(BLK_MQ_MAX_DISPATCH_ORDER - 1, ilog2(queued) + 1);
}

-static bool __blk_mq_get_driver_tag(struct request *rq)
+static bool __blk_mq_alloc_driver_tag(struct request *rq)
{
struct sbitmap_queue *bt = &rq->mq_hctx->tags->bitmap_tags;
unsigned int tag_offset = rq->mq_hctx->tags->nr_reserved_tags;
@@ -1159,11 +1159,9 @@ static bool __blk_mq_get_driver_tag(struct request *rq)
return true;
}

-bool blk_mq_get_driver_tag(struct request *rq)
+bool __blk_mq_get_driver_tag(struct blk_mq_hw_ctx *hctx, struct request *rq)
{
- struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
-
- if (rq->tag == BLK_MQ_NO_TAG && !__blk_mq_get_driver_tag(rq))
+ if (rq->tag == BLK_MQ_NO_TAG && !__blk_mq_alloc_driver_tag(rq))
return false;

if ((hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED) &&
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 8be447995106..ceed0a001c76 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -264,7 +264,20 @@ static inline void blk_mq_put_driver_tag(struct request *rq)
__blk_mq_put_driver_tag(rq->mq_hctx, rq);
}

-bool blk_mq_get_driver_tag(struct request *rq);
+bool __blk_mq_get_driver_tag(struct blk_mq_hw_ctx *hctx, struct request *rq);
+
+static inline bool blk_mq_get_driver_tag(struct request *rq)
+{
+ struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
+
+ if (rq->tag != BLK_MQ_NO_TAG &&
+ !(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
+ hctx->tags->rqs[rq->tag] = rq;
+ return true;
+ }
+
+ return __blk_mq_get_driver_tag(hctx, rq);
+}

static inline void blk_mq_clear_mq_map(struct blk_mq_queue_map *qmap)
{
--
2.33.0