cdc oom when sysbench prepare to create 1000 tables

[Tammyxia]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do? If possible, provide a recipe for reproducing the error.

• Create changefeed with filter one database.
• Run sysbench to create tables "# sysbench oltp_common prepare --db-driver=mysql --mysql-host=172.16.6.13 --mysql-port=3306 --mysql-user=root --mysql-password= --mysql-db=tammy --threads=512 --tables=1000 --table-size=0"

2. What did you expect to see?

• sync task completed without any error

3. What did you see instead?

• sync task complete, but cdc oom:
  

4. Versions of the cluster

   • Upstream TiDB cluster version (execute SELECT tidb_version(); in a MySQL client):

     5.0.2
     

   • TiCDC version (execute cdc version):

     5.0.2
     

[Tammyxia]

cdc server: cpu 8c, memory 16GB.

[amyangfei]

We have optimized the memory usage under 16G host ref: https://github.com/pingcap/ticdc/pull/1915, https://github.com/pingcap/ticdc/pull/1999