How to interpret view pg_stat_bgwriter

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Hi,

 

Sorry for send this email twice but it seems it fits the performance group than admin group…

 

I was reading an article of Gregory Smith http://www.westnet.com/~gsmith/content/postgresql/chkp-bgw-83.htm and tried to do some analysis on our database.

 

postgres=#  select * from pg_stat_bgwriter;

-[ RECORD 1 ]------+------------

checkpoints_timed  | 42435

checkpoints_req    | 629448

buffers_checkpoint | 1821978480

buffers_clean      | 117710078

maxwritten_clean   | 23796

buffers_backend    | 1284631340

buffers_alloc      | 32829025268

 

postgres=# show checkpoint_segments ;

-[ RECORD 1 ]-------+----

checkpoint_segments | 128

 

 

postgres=# show checkpoint_timeout ;

-[ RECORD 1 ]------+------

checkpoint_timeout | 10min

 

bgwriter_delay           bgwriter_lru_maxpages    bgwriter_lru_multiplier

postgres=# show bgwriter_delay;

-[ RECORD 1 ]--+------

bgwriter_delay | 100ms

 

postgres=# show bgwriter_lru_maxpages;

-[ RECORD 1 ]---------+-----

bgwriter_lru_maxpages | 1000

 

postgres=# show bgwriter_lru_multiplier;

-[ RECORD 1 ]-----------+--

bgwriter_lru_multiplier | 5

 

based on one snapshot, below are my thoughts after reading the example reading the example Greg used, it might be completely wrong as I’m just starting the learning process of checkpoint mechanism in PG.  If anything missing/wrong, appreciate if you can help to point out.

 

# checkpoints_req is much bigger than checkpoints_timed, suggest that I may increase checkpoint_segments in our system

#maxwritten_clean is high, suggests increase bgwriter_lru_maxpages

# buffers_backend is much smaller than buffers_alloc, suggests increasing bgwriter_lru_maxpages, bgwriter_lru_multiplier, and decreasing bgwriter_delay.

 

 

Thanks,

Suya

 


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