Re: Let PostgreSQL's On Schedule checkpoint write buffer smooth spread cycle by tuning IsCheckpointOnSchedule?

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, digoal zhou <digoal(dot)zhou(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Let PostgreSQL's On Schedule checkpoint write buffer smooth spread cycle by tuning IsCheckpointOnSchedule?
Date: 2015-07-03 07:48:20
Message-ID: alpine.DEB.2.10.1507030930070.16176@sto
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> power 1,5 is almost certainly not right for all cases, but it is simple
> and better.

It is better "in some cases", as I've been told on my patch. If you have a
separate disk for WAL writes the power formula may just degrade
performance, or maybe not, or not too much, or it really should be a guc.

Well, I just think that it needs more performance testing with various
loads and sizes, really. I'm not against this patch at all.

> And easy to remove if something even better arrives.
>
> I don't see the two patches being in conflict.

They are not "in conflict" from a git point of view, or even so it would
be trivial to solve.

They are in conflict as the patch changes the checkpoint load
significantly, which would mean that my X00 hours of performance testing
on the checkpoint scheduler should more or less be run again. Ok, it is
somehow egoistic, but I'm trying to avoid wasting people time.

Another point is that I'm not sure I understand the decision process: for
some patch in some area extensive performance tests are required, and for
other patches in the same area they would not be.

--
Fabien.

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