changefeed lag reached more than 21 mins during upgrading from 6.5.11 to 8.5.0

[Lily2025]

What did you do?

1、run many MVCC workload on 6.5.11
2、create changefeed (downstream: kafka)
3、upgrade from 6.5.11 to 8.5.0

What did you expect to see?

changefeed lag is normal during upgrading

What did you see instead?

changefeed lag reached more than 21 mins during upgrading

Versions of the cluster

Upstream TiDB cluster version (execute SELECT tidb_version(); in a MySQL client):
sh-5.1# ./tidb-server -V
Release Version: v8.5.0
Edition: Community
Git Commit Hash: d13e52ed6e22cc5789bed7c64c861578cd2ed55b
Git Branch: HEAD
UTC Build Time: 2024-12-18 02:26:06
GoVersion: go1.23.3
Race Enabled: false
Check Table Before Drop: false
Store: unistore

Upstream TiKV version (execute tikv-server --version):
sh-5.1# ./tikv-server -V
TiKV
Release Version: 8.5.0
Edition: Community
Git Commit Hash: a2c58c94f89cbb410e66d8f85c236308d6fc64f0
Git Commit Branch: HEAD
UTC Build Time: 2024-12-18 03:28:49
Rust Version: rustc 1.77.0-nightly (89e2160c4 2023-12-27)
Enable Features: memory-engine pprof-fp jemalloc mem-profiling portable sse test-engine-kv-rocksdb test-engine-raft-raft-engine trace-async-tasks openssl-vendored
Profile: dist_release

TiCDC version (execute `cdc version`):
sh-5.1# ./cdc version   
Release Version: v8.5.0
Git Commit Hash: 3703b18c6da785d57236a1452eed43759e51b411
Git Branch: HEAD
UTC Build Time: 2024-12-17 04:34:05
Go Version: go1.23.3
Failpoint Build: false
sh-5.1# 

[Lily2025]

/severity major
/assign hongyunyan