Re: CLOG contention

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Robert Haas" <robertmhaas(at)gmail(dot)com>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: CLOG contention
Date: 2011-12-21 15:51:40
Message-ID: 4EF1AC2C0200002500043F3D@gw.wicourts.gov
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Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> Any thoughts on what makes most sense here? I find it fairly
> tempting to just crank up NUM_CLOG_BUFFERS and call it good,

The only thought I have to add to discussion so far is that the need
to do anything may be reduced significantly by any work to write
hint bits more aggressively. We only consult CLOG for tuples on
which hint bits have not yet been set, right? What if, before
writing a page, we try to set hint bits where we can? When
successful, it would not only prevent one or more later writes of
the page, but could also prevent having to load old CLOG pages.
Perhaps the hint bit issue should be addressed first, and *then* we
check whether we still have a problem with CLOG.

-Kevin

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