From: Peter Childs <peterachilds@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Long Running Commits - Not Checkpoints
Date: Fri, 14 Sep 2007 08:42:59 +0100
Message-ID: <a2de01dd0709140042j386ea27lbf1f4d3f89b543ff@mail.gmail.com> (raw)
In-Reply-To: <a2de01dd0709140002m54946c6bte398944bee8b2eaa@mail.gmail.com>
References: <1189692915.8624.22.camel@bnicholson-desktop>
<Pine.GSO.4.64.0709131149390.20144@westnet.com>
<1189700385.8624.32.camel@bnicholson-desktop>
<Pine.GSO.4.64.0709131339450.21671@westnet.com>
<a2de01dd0709140002m54946c6bte398944bee8b2eaa@mail.gmail.com>
On 14/09/2007, Peter Childs <peterachilds@gmail.com> wrote:
>
>
>
> On 13/09/2007, Greg Smith <gsmith@gregsmith.com> wrote:
> >
> >
> > Every time the all scan writes a buffer that is frequently used, that
> > write has a good chance that it was wasted because the block will be
> > modified again before checkpoint time. Your settings are beyond regular
> >
> > aggressive and into the hyperactive terrority where I'd expect such
> > redundant writes are happening often. I'd suggest you try to move
> > toward
> > dropping bgwriter_all_percent dramatically from its current setting and
> > see how far down you can go before it starts to introduce blocks at
> > checkpoint time. With bgwriter_delay set to 1/4 the default, I would
> > expect that even 5% would be a high setting for you. That may be a more
> > dramatic change than you want to make at once though, so lowering it in
> > that direction more slowly (perhaps drop 5% each day) and seeing whether
> > things improve as that happens may make more sense.
> >
> >
> Are you suggesting that reducing bgwriter_delay and bg_writer_percent
> would reduce the time spent doing commits?
>
> I get quite a few commits that take over 500ms (the point when i start
> logging queries). I always thought oh just one of those things but if they
> can be reduced by changing a few config variables that would be great. I'm
> just trying to workout what figures are worth trying to see if I can reduce
> them.
>
> From time to time I get commits that take 6 or 7 seconds but not all the
> time.
>
> I'm currently working with the defaults.
>
> Peter Childs
>
Hmm Always read the manual, Increase them from the defaults.......
Peter.
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To: pgsql-performance@postgresql.org
Cc: peterachilds@gmail.com
Subject: Re: Long Running Commits - Not Checkpoints
In-Reply-To: <a2de01dd0709140042j386ea27lbf1f4d3f89b543ff@mail.gmail.com>
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