| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> |
| Cc: | Josh Berkus <josh(at)agliodbs(dot)com>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: postgresql latency & bgwriter not doing its job |
| Date: | 2014-08-26 08:18:18 |
| Message-ID: | 20140826081818.GF21544@awork2.anarazel.de |
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| Lists: | pgsql-hackers |
On 2014-08-26 08:12:48 +0200, Fabien COELHO wrote:
> As for checkpoint spreading, raising checkpoint_completion_target to 0.9
> degrades the situation (20% of transactions are more than 200 ms late
> instead of 10%, bgwriter wrote less that 1 page per second, on on 500s run).
> So maybe there is a bug here somewhere.
What are the other settings here? checkpoint_segments,
checkpoint_timeout, wal_buffers?
Could you show the output of log_checkpoints during that run? Checkpoint
spreading only works halfway efficiently if all checkpoints are
triggered by "time" and not by "xlog".
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
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