08-18 performance regression on a bench_upay_178

[mahjonp]

Bug Report

There is a 4% performance regression on bench_upay_178

1. What did you do?

Version:
tidb: 92513a2f4d382dc89bb47d3907261d49175f20ac(master) 2020-08-18 14:13:51
tikv: 4547ac41e784ec7a9a119a5fd0d83140ae565d57(master) 2020-08-17 10:26:31
pd: 18cd59e0c5b2af17f8263f80ae79936091c14d6b(master) 2020-08-18 12:38:02

Compare:
tidb: https://github.com/pingcap/tidb/compare/67214e7...92513a2
tikv: https://github.com/tikv/tikv/compare/4547ac4...4547ac4
pd: https://github.com/pingcap/pd/compare/18cd59e...18cd59e

tidb_max_cpu: 21.83, delta: -0.61%
tikv_max_cpu: 1.47, delta: -2.87%
tidb_max_memory: 350.24 MiB, delta: 1.36%
tikv_max_memory: 1417.89 MiB, delta: -1.00%

tps: 2926.25 ± 0.6805% (std=13.20) delta: -4.20%
qps: 11705.01 ± 0.6807% (std=52.83) delta: -4.20%
lat_avg: 87.48 ± 0.6773% (std=0.39) delta: 4.38%
lat_99th: 269.37 ± 2.4991% (std=3.86) delta: 4.43%

2. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?

92513a2