loadInfoSchema() slow when there are background query visiting INFORMATION_SCHEMA.TABLES

[tiancaiamao]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1M table in the cluster already, run 'create table' workload together with a "SELECT TABLE_NAME FROM information_schema.TABLES WHERE TABLE_SCHEMA = xxx' workload.

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

DDL should be fast enough.

3. What did you see instead (Required)

DDL is slow, and the LoadSchemaDiff takes a long time.

4. What is your TiDB version? (Required)

master

commit dde1dcd750d3037c8f4576d8bcca716a1b91cd09 (HEAD -> master, origin/master, origin/HEAD)
Author: Rustin <tech@rustin.me>
Date:   Tue Dec 17 18:05:42 2024 +0800

    session: add indexes for `mysql.analyze_jobs` (#58134)
    
    close pingcap/tidb#57996

[tiancaiamao]

It could be caused by the mutex lock contention.

Visiting INFORMATION_SCHEMA.TABLES hold the lock for a long time.
LoadSchemaDiff need to rebuild schema and add new record to the btree.
They conflicts.