Add mintso config parameters (#19452)

Author: xzhangxian1008

tiflash/tiflash-configuration.md

@@ -264,6 +264,15 @@ delta_index_cache_size = 0
     ## New in v7.4.0. This item controls whether to enable the TiFlash resource control feature. When it is set to true, TiFlash uses the pipeline execution model.
     enable_resource_control = true
 
+    ## New in v6.0.0. This item is used for the MinTSO scheduler. It specifies the maximum number of threads that one resource group can use. The default value is 5000. For details about the MinTSO scheduler, see https://docs.pingcap.com/tidb/dev/tiflash-mintso-scheduler.
+    task_scheduler_thread_soft_limit = 5000
+
+    ## New in v6.0.0. This item is used for the MinTSO scheduler. It specifies the maximum number of threads in the global scope. The default value is 10000. For details about the MinTSO scheduler, see https://docs.pingcap.com/tidb/dev/tiflash-mintso-scheduler.
+    task_scheduler_thread_hard_limit = 10000
+
+    ## New in v6.4.0. This item is used for the MinTSO scheduler. It specifies the maximum number of queries that can run simultaneously in a TiFlash instance. The default value is 0, which means twice the number of vCPUs. For details about the MinTSO scheduler, see https://docs.pingcap.com/tidb/dev/tiflash-mintso-scheduler.
+    task_scheduler_active_set_soft_limit = 0
+
 ## Security settings take effect starting from v4.0.5.
 [security]
     ## New in v5.0. This configuration item enables or disables log redaction. Value options: `true`, `false`, `"on"`, `"off"`, and `"marker"`. The `"on"`, `"off"`, and `"marker"` options are introduced in v8.2.0.

tiflash/tiflash-mintso-scheduler.md

@@ -62,3 +62,7 @@ The scheduling process of the MinTSO Scheduler is as follows:
 ![TiFlash MinTSO Scheduler v2](/media/tiflash/tiflash_mintso_v2.png)
 
 By introducing soft limit and hard limit, the MinTSO scheduler effectively avoids system deadlock while controlling the number of system threads. In high concurrency scenarios, however, most queries might only have part of their MPP tasks scheduled. Queries with only part of MPP tasks scheduled cannot execute normally, leading to low system execution efficiency. To avoid this situation, TiFlash introduces a query-level limit for the MinTSO scheduler, called active_set_soft_limit. This limit allows only MPP tasks of up to active_set_soft_limit queries to participate in scheduling; MPP tasks of other queries do not participate in scheduling, and only after the current queries finish can new queries participate in scheduling. This limit is only a soft limit because for the MinTSO query, all its MPP tasks can be scheduled directly as long as the number of system threads does not exceed the hard limit.
+
+# See also
+
+- [Configure TiFlash](/tiflash/tiflash-configuration.md): learn how to configure the MinTSO scheduler.