From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Maksym Boguk <maxim(dot)boguk(at)gmail(dot)com> |
Cc: | pgsql-bugs(at)postgresql(dot)org |
Subject: | Re: BUG #6296: High level backend-write activity on db |
Date: | 2011-11-17 04:43:14 |
Message-ID: | CA+TgmoZZ_UiFM9omaRhAsaAv+Sx6hzjcZS7tKHZzmtZfnx1wJw@mail.gmail.com |
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Lists: | pgsql-bugs |
On Wed, Nov 16, 2011 at 4:07 AM, Maksym Boguk <maxim(dot)boguk(at)gmail(dot)com> wrote:
> Again I not sure it is actual bug or something else go wrong with my
> database.
>
> One of my databases just started produce 256 wal segments in 5 minutes
> instead of 100-200 wal segments per hour (averages).
>
> In the same time write and read activity on DB stay same (according to the
> pg_stat_database data and historical graphs).
> No anti-wraparound vacuum and such things going on.
> Situation staying same during last few days.
>
>
> I found some other anomalies:
> 1)5 minutes after
> SELECT pg_stat_reset_shared('bgwriter');
>
> mirtesen=# SELECT * from pg_stat_bgwriter ;
> checkpoints_timed | checkpoints_req | buffers_checkpoint | buffers_clean |
> maxwritten_clean | buffers_backend | buffers_alloc
> -------------------+-----------------+--------------------+---------------+-
> -----------------+-----------------+---------------
> 0 | 2 | 171675 | 804 |
> 0 | 1010429 | 1131106
> (1 row)
>
> eg almost any new buffer allocated by backend leading to backend write out
> dirty page (and that situation do not change overtime).
This sure sounds like a ring buffer is being used, suggesting VACUUM
or COPY IN activity.
What does pg_stat_activity say?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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