From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Heavy write activity on first vacuum of fresh TOAST data |
Date: | 2007-12-13 19:20:43 |
Message-ID: | 1197573643.4255.1877.camel@ebony.site |
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Lists: | pgsql-performance |
On Thu, 2007-12-13 at 13:52 -0500, Tom Lane wrote:
> Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
> > Simon Riggs wrote:
> >> We might be able to have bgwriter set hint bits on dirty blocks,
>
> > I don't think that works, because the bgwriter has no access to the
> > catalogs, therefore it cannot examine the page contents. To bgwriter,
> > pages are opaque.
>
> Another issue is that this'd require bgwriter to access the clog SLRU
> area. I seem to remember worrying that that could lead to low-level
> deadlocks, though I cannot recall the exact case at the moment.
> Even without that, it would increase contention for SLRU, which we
> probably don't want.
I was trying to highlight the problems, not advocate that as an
approach, sorry if I wasn't clear enough. Even if you solved the
problems both of you have mentioned I don't think the dynamic behaviour
will be useful enough to merit the effort of trying. I'm definitely not
going to be spending any time on this. Fish are frying elsewhere.
--
Simon Riggs
2ndQuadrant http://www.2ndQuadrant.com
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