DML sql execution time slow down PGv14 compared with PGv13

Hi,

   We had some load test ( DML inserts/deletes/updates)  and found that PGV14 slow down 10-15% compared with PGV13.  Same test server, same schema tables and data. From pg_stat_statements, sql exec_time, we did found similar mean_exec_time increased from 20%-30% with same SQL statements. Both v14 and v13 give very fast sql response time, just compare the %diff from sql statements mean_exec_time.

   Now, I get a pgbench test in same server, the steps as below, small sql statement running very fast, not like our application load test that show INSERTS slow down 20-30%, but did see v14 slow down 5-10% for DML,compared with v13.

   1.date;pgbench -i -s 6000 -F 85 -U pgbench --partition-method=hash --partitions=32

   2.reboot OS to refresh buffer

   3.run four rounds of test:  date;pgbench -c 10 -j 10 -n -T 180 -U pgbench -M prepared

Compare 14.6 and 13.9 on RHEL8.4,  the “add primary key” step 14.6 much fast than 13.9, but most of insert/updates slow down 5-10%.  The table is very simple and sql should be same, no idea what contribute to the sql exec_time difference?  Attached please find sql exec_time.

I copy the sql here too,

Thanks,

James