psql postgres <<EOF
drop table if exists xlogpos;
create table xlogpos(oldpos text);
EOF
./contrib/pgbench/pgbench_for_hot_update -i postgres 
psql postgres -c checkpoint
psql postgres -c "insert into xlogpos values (pg_current_xlog_insert_location());"
./contrib/pgbench/pgbench_for_hot_update -n -t 100000 postgres
psql postgres -c "select pg_xlog_location_diff(pg_current_xlog_insert_location(), oldpos) from xlogpos"