Re: Fix for erroneous warning on Shutdown - Mailing list pgsql-patches

From Bruce Momjian
Subject Re: Fix for erroneous warning on Shutdown
Date
Msg-id 200406160250.i5G2o3N08914@candle.pha.pa.us
Whole thread Raw
In response to Re: Fix for erroneous warning on Shutdown  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-patches
Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.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.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

pgsql-patches by date:

Previous
From: Tom Lane
Date:
Subject: Re: Fix for erroneous warning on Shutdown
Next
From: "Matthew T. O'Connor"
Date:
Subject: pg_autovacuum integration patch