single thread throughput drops when enabling data cache

Alluxio Version: 2.9.0

Describe the bug

compared with the time-consuming loading of dataset under single concurrency, we can find that single thread throughput drops when enabling data cache.

fuse data cache off (issue-17025), 1 concurrent time cost: 83s fuse data cache on (issue-17026), 1 concurrent time cost: 122s

Expected behavior

single thread slightly (<10%) throughput drops when enabling data cache