blk-mq: save queue mapping result into ctx directly

Currently, the queue mapping result is saved in a two-dimensional
array. In the hot path, to get a hctx, we need do following:

  q->queue_hw_ctx[q->tag_set->map[type].mq_map[cpu]]

This isn't very efficient. We could save the queue mapping result into
ctx directly with different hctx type, like,

  ctx->hctxs[type]

Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 4 insertions, 3 deletions

diff --git a/block/blk-mq.h b/block/blk-mq.h
index d943d46b0785..9fb06261518e 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -23,6 +23,7 @@ struct blk_mq_ctx {
 
         unsigned int            cpu;
         unsigned short          index_hw[HCTX_MAX_TYPES];
+        struct blk_mq_hw_ctx    *hctxs[HCTX_MAX_TYPES];
 
         /* incremented at dispatch time */
         unsigned long           rq_dispatched[2];
@@ -97,11 +98,11 @@ static inline struct blk_mq_hw_ctx *blk_mq_map_queue_type(struct request_queue *
  * blk_mq_map_queue() - map (cmd_flags,type) to hardware queue
  * @q: request queue
  * @flags: request command flags
- * @cpu: CPU
+ * @cpu: cpu ctx
  */
 static inline struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *q,
                                                      unsigned int flags,
-                                                     unsigned int cpu)
+                                                     struct blk_mq_ctx *ctx)
 {
         enum hctx_type type = HCTX_TYPE_DEFAULT;
 
@@ -116,7 +117,7 @@ static inline struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *q,
                  q->tag_set->map[HCTX_TYPE_READ].nr_queues)
                 type = HCTX_TYPE_READ;
         
-        return blk_mq_map_queue_type(q, type, cpu);
+        return ctx->hctxs[type];
 }
 
 /*