tidb: add general-log-file and compression

tidb-configuration-file.md

@@ -319,6 +319,12 @@ Configuration items related to log.
 - Default value: `10000`
 - When the number of query rows (including the intermediate results based on statistics) is larger than this value, it is an `expensive` operation and outputs log with the `[EXPENSIVE_QUERY]` prefix.
 
+### `general-log-file` <span class="version-mark">New in v8.0.0</span>
+
++ The file name of the [general log](/system-variables.md#tidb_general_log).
++ Default value: ""
++ If you specify a file name, the general log is written to this particular file. If the value is blank, the general log is written to the server log of the TiDB instance. The name of server log is specified by [`filename`](#filename). 
+
 ### `timeout` <span class="version-mark">New in v7.1.0</span>
 
 - Sets the timeout for log-writing operations in TiDB. In case of a disk failure that prevents logs from being written, this configuration item can trigger the TiDB process to panic instead of hang.
@@ -355,6 +361,12 @@ Configuration items related to log files.
 - Default value: `0`
 - All the log files are retained by default. If you set it to `7`, seven log files are retained at maximum.
 
+#### `compress` <span class="version-mark">New in v8.0.0</span>
+
++ The compression method for the log.
++ Default value: ""
++ By default, compression is not enabled. Currently, the only supported compression format is `"gzip"`. After compression is enabled, all log files are affected, such as `slow-log-file` and `general-log-file`.
+
 ## Security
 
 Configuration items related to security.