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Re: [HACKERS] pg_stat_wal_write statistics view - Mailing list pgsql-hackers

From Haribabu Kommi
Subject Re: [HACKERS] pg_stat_wal_write statistics view
Date
Msg-id CAJrrPGcvjDuju9Qv2Q7E1Oqby8ZOPc4e3NJiKpCuL4aR-rudBw@mail.gmail.com
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In response to Re: [HACKERS] pg_stat_wal_write statistics view  (Peter Eisentraut <peter.eisentraut@2ndquadrant.com>)
Responses Re: [HACKERS] pg_stat_wal_write statistics view
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On Tue, Aug 15, 2017 at 7:39 AM, Peter Eisentraut <peter.eisentraut@2ndquadrant.com> wrote:
On 3/29/17 22:10, Haribabu Kommi wrote:
> Updated patch to use shared counter instead of adding pg_stat_ calls to send
> the statistics from each background process/worker.

Your patch needs to be rebased and the OID assignments updated.

Rebased patch is attached. And also it has taken care of the comments provided
by Andres and Fuji Masao in the upthread.

I separated the walwriter statistics from the other background processes to check
how much load does the other processes are really contributing to wal writing.

Following is the test results during my performance test.

 writes | walwriter_writes | backend_writes | dirty_writes | walwriter_dirty_writes | backend_dirty_writes | write_blocks | walwriter_write_blocks | backend_write_blocks | write_time | walwriter_write_time | backend_write_time | sync_time | walwriter_sync_time | backend_sync_time |          stats_reset          
--------+------------------+----------------+--------------+------------------------+----------------------+--------------+------------------------+----------------------+------------+----------------------+--------------------+-----------+---------------------+-------------------+-------------------------------
      0 |         17748394 |     1383789657 |            0 |                      0 |                    0 |            0 |               21153194 |           3039806652 |          0 |                    0 |                  0 |         0 |           259250230 |       17262560725 | 2017-09-05 18:22:41.087955+10
(1 row)

I didn't find any other background processes contribution to the WAL writing activity.
May be we can combine them with backend stats?

I ran the performance test on this patch with pgbench to find out the impact of these
changes. Because of my low end machine, the performance results are varying too
much, I will try to get the performance figures from an high end machine by that time.

Attached the latest patch and performance report.

Regards,
Hari Babu
Fujitsu Australia
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