How to configure postgresql-9.2 to know blk_write_time in pg_stat_database Interested in the procedure for collecting block write statistics of PostgreSQL 9.2.

Steps followed for configuration, could get blk_read time but not blk_write_time


CREATE EXTENSION adminpack; and CREATE EXTENSION dblink;
Changed postgresql.conf file

# - Query/Index Statistics Collector -

track_activities = on
track_counts = on
track_io_timing = on
track_functions = all           # none, pl, all
track_activity_query_size = 1024    # (change requires restart)
update_process_title = on
stats_temp_directory = 'pg_stat_tmp'

# - Background Writer -

bgwriter_delay = 200ms          # 10-10000ms between rounds
bgwriter_lru_maxpages = 100     # 0-1000 max buffers written/round
bgwriter_lru_multiplier = 2.0       # 0-10.0 multipler on buffers scanned/round

Restarted Postgres Server
Performed around 2000 inserts to table
But could not view the blk_write_time.
configuration above is correct. Before viewing the blk_write_time, do a vacuum. If you still see a 0 try increasing the inserts from 2000 to say 1000000.

Step 5: 
vacuum;
Step 6:
select datname, blk_write_time from pg_stat_database;