PostgreSQL- Performance deviation on run same test and workload on multiple trails

[anilbommareddy]

PostgreSQLv14 source code compiled with GCCv11 and binaries' installed in /usr/test/pgsqlv14-gcc.
Run TPC-C tests with HammerDB scripts.
OS: RHEL 8.4
HammerDBv4.2

steps are followed

umount /usr/local/pgsql/data
rm -rf /usr/local/pgsql/data
mkdir /usr/local/pgsql/data
mkfs.xfs -f /dev/nvme0n1
mount /dev/nvme0n1 /usr/local/pgsql/data
chown postgres /usr/local/pgsql/data
2.
su - postgres
Export Environment Variable's of of pgsqlv14-gcc

export PATH=/usr/test/pgsqlv14-gcc/bin:$PATH
export LD_LIBRARY_PATH=/usr/test/pgsqlv14-gcc/lib:$LD_LIBRARY_PATH

commands to run:

initdb -D /usr/local/pgsql/data
pg_ctl start -D /usr/local/pgsql/data

HammerDBv4.2 test:

(a) build_schema warehouse 500 and vu50.
(b)On schema done successfully restart postgresql
(c)run the test for vu's like:192vu and 250vu
Virtual Users trail-1 trail-2
192 1172413 1578301 difference trail1vs trail2 >20%
250 828171 494046 difference >20%

After trail-1 was done.
drop data base tpc-c in postgresql
restart postgresql
Run build_schema and schemd done succesfully.
restart postgresql
run the tests -2nd trail

As per HammerDB documents for multiple test runs the deviation expected is 1-2%
Here Observed trail-1 and trail-2 deviation is more than 20% for 192vu and 250vu

Reference links:
https://www.enterprisedb.com/how-to-benchmark-postgresql-using-hammerdb-open-source-tool (hammerdb scripts)