Re: Do you know the reason for increased max latency due to xlog scaling?

On 2014-02-18 01:35:52 +0900, MauMau wrote:
> From: "Andres Freund" <andres(at)2ndquadrant(dot)com>
> >On 2014-02-18 00:43:54 +0900, MauMau wrote:
> >>I'm worried about the big increase in max latency. Do you know the
> >>cause?
> >>More frequent checkpoints caused by increased WAL volume thanks to
> >>enhanced
> >>performance?
> >
> >I don't see much evidence of increased latency there? You can't really
> >compare the latency when the throughput is significantly different.
>
> For example, please see the max latencies of test set 2 (PG 9.3) and test
> set 4 (xlog scaling with padding). They are 207.359 and 1219.422
> respectively. The throughput is of course greatly improved, but I think the
> response time should not be sacrificed as much as possible. There are some
> users who are sensitive to max latency, such as stock exchange and online
> games.

You need to compare both at the same throughput to have any meaningful
comparison.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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