[next gen on clould] connection count can not balance after tidb memory increased

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1、run batch insert

2. What did you expect to see? (Required)

connection count can balance

3. What did you see instead (Required)

connection count can not balanced after tidb memory increased

4. What is your version? (Required)

mysql> select distinct concat('[',type,']') component_type, concat('version:',version,',') version,concat('git_hash:',git_hash) git_hash from information_schema.cluster_info;
+-------------------+----------------------------------------------+---------------------------------------------------+
| component_type | version | git_hash |
+-------------------+----------------------------------------------+---------------------------------------------------+
| [tiflash_compute] | version:9.0.0-beta.2.pre-79-gc68b24e1a, | git_hash:c68b24e1a901797f84d01bf9b950fb776597d418 |
| [tidb] | version:8.5.4-nextgen.202510.0-7-gc634954, | git_hash:c634954c6ea64c0d4547b5273e92421cca2cb12e |
| [pd] | version:8.5.4-nextgen.202510.1-1-gf912cdd, | git_hash:f912cdd1e9cdae8d4927b888545e6f003bea375a |
| [tso] | version:8.5.4-nextgen.202510.1-1-gf912cdd, | git_hash:f912cdd1e9cdae8d4927b888545e6f003bea375a |
| [scheduling] | version:8.5.4-nextgen.202510.1-1-gf912cdd, | git_hash:f912cdd1e9cdae8d4927b888545e6f003bea375a |
| [tikv] | version:8.5.0, | git_hash:15e3ce20089cc5ec97e2f07a5880cf6f732c0780 |
| [tiflash_write] | version:8.5.4-nextgen.202510.0-3-g492b32cd2, | git_hash:492b32cd2f8576cc3cfd4bc1bf936060c9c7cfe7 |
+-------------------+----------------------------------------------+---------------------------------------------------+
7 rows in set (0.09 sec)

mysql>

No source files or tests are named. Reproduce the issue with a batch insert, then compare connection counts before and after increasing TiDB memory using the listed cluster versions; done means the connection count balances as expected.