Re: Fix for erroneous warning on Shutdown

Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Tom Lane wrote:
> >> ... The question stands though: why isn't it
> >> appropriate to warn of overly-frequently-issued manual checkpoints?
>
> > ... the warning is for cases when you are filling up the WAL logs too
> > quickly and checkpoints are happening too frequently. If a user is
> > doing checkpoints, it isn't anything increasing the checkpoint segments
> > is going to help.
>
> No, I think the warning is for when checkpoints are happening too
> frequently, period. An overly small checkpoint_segments setting
> is one possible cause of that, but the performance penalty from
> too many checkpoints is just as bad no matter what's causing it.
> (Remember that a checkpoint not only forces I/O in itself, but
> significantly increases subsequent WAL traffic because of needing
> to dump whole page images into WAL.)
>
> How do you feel about improving the signaling mechanism but using
> it just to vary the HINT?
>
> LOG: checkpoints are occurring too frequently (nn seconds apart)
> HINT: Consider increasing the configuration parameter "checkpoint_segments".
>
> LOG: checkpoints are occurring too frequently (nn seconds apart)
> HINT: Issuing explicit CHECKPOINTs so often is really expensive.

Sure, fine by me. My only point is that we need something to tell
people they need to increase their checkpoint_segments. If we add other
warnings, that is fine too.

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