–concurrency uint32 The size of a BR thread pool that executes tasks, One task represents one table range (or one index range) according to the backup schemas. If there is one table with one index.there will be two tasks to back up this table. This value should increase if you need to back up lots of tables or indices. (default 4)
用于 BR 备份相关的配置项。
num-threads
处理备份的工作线程数量。
默认值：CPU * 0.5，但最大为 8
可调整范围：[1, CPU]
最小值：1
这两个参数怎么理解
是不是总分的关系。