tikv: update default settings of server.grpc-concurrency and server.grpc-raft-conn-num.

tikv-configuration-file.md

@@ -151,7 +151,10 @@ This document only describes the parameters that are not included in command-lin
 ### `grpc-concurrency`
 
 + The number of gRPC worker threads. When you modify the size of the gRPC thread pool, refer to [Performance tuning for TiKV thread pools](/tune-tikv-thread-performance.md#performance-tuning-for-tikv-thread-pools).
-+ Default value: `5`
++ Default value: From v8.5.4 and v9.0.0, adjusted to `grpc-raft-conn-num * 3 + 2`. The default value of `grpc-raft-conn-num` can be referenced from [`grpc-raft-conn-num`](#grpc-raft-conn-num). In v8.5.3 and earlier versions, the default value is 5.
++
++    + For example, when the number of CPU cores is 8, the default value of `grpc-raft-conn-num` is 1, and accordingly, the default value of `grpc-concurrency` is `1 * 3 + 2 = 5`.
++
 + Minimum value: `1`
 
 ### `grpc-concurrent-stream`
@@ -169,7 +172,7 @@ This document only describes the parameters that are not included in command-lin
 ### `grpc-raft-conn-num`
 
 + The maximum number of connections between TiKV nodes for Raft communication
-+ Default value: `1`
++ Default value: From v8.5.4 and v9.0.0, adjusted to `MAX(1, MIN(4, CPU cores / 8))`. Here, `MIN(4, CPU cores / 8)` indicates that when the number of CPU cores is greater than or equal to 32, the default maximum number of connections is 4. In v8.5.3 and earlier versions, the default value is 1.
 + Minimum value: `1`
 
 ### `max-grpc-send-msg-len`