Re: Just-in-time Background Writer Patch+Test Results

On Thu, Sep 06, 2007 at 09:20:31AM -0500, Kevin Grittner wrote:
> >>> On Wed, Sep 5, 2007 at 10:31 PM, in message
> <Pine(dot)GSO(dot)4(dot)64(dot)0709052324020(dot)25284(at)westnet(dot)com>, Greg Smith
> <gsmith(at)gregsmith(dot)com> wrote:
> >
> > -There are two magic constants in the code:
> >
> > int smoothing_samples = 16;
> > float scan_whole_pool_seconds = 120.0;
> >
>
> > I personally
> > don't feel like these constants need to be exposed for tuning purposes;
>
> > Determining
> > whether these should be exposed as GUC tunables is certainly an open
> > question though.
>
> If you exposed the scan_whole_pool_seconds as a tunable GUC, that would
> allay all of my concerns about this patch. Basically, our problems were

I like the idea of not having that as a GUC, but I'm doubtful that it
can be hard-coded like that. What if checkpoint_timeout is set to 120?
Or 60? Or 2000?

I don't know that there should be a direct correlation, but ISTM that
scan_whole_pool_seconds should take checkpoint intervals into account
somehow.
--
Decibel!, aka Jim Nasby decibel(at)decibel(dot)org
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