| From: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, MauMau <maumau307(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Do you know the reason for increased max latency due to xlog scaling? |
| Date: | 2014-02-18 21:01:08 |
| Message-ID: | 5303CA14.8070806@vmware.com |
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| Lists: | pgsql-hackers |
On 02/18/2014 10:51 PM, Andres Freund wrote:
> On 2014-02-18 19:12:32 +0200, Heikki Linnakangas wrote:
>> Yeah, I'm pretty sure that's because of the extra checkpoints. If you look
>> at the individual test graphs, there are clear spikes in latency, but the
>> latency is otherwise small. With a higher TPS, you reach checkpoint_segments
>> quicker; I should've eliminated that effect in the tests I ran...
>
> I don't think that'd be a good idea. The number of full page writes so
> greatly influences the WAL charactersistics, that changing checkpoint
> segments would make the tests much harder to compare.
I was just thinking of bumping up checkpoint_segments so high that there
are no checkpoints during any of the tests.
- Heikki
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