Re: limiting hint bit I/O

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: <robertmhaas(at)gmail(dot)com>
Cc: <josh(at)agliodbs(dot)com>,<pgsql-hackers(at)postgresql(dot)org>, <tgl(at)sss(dot)pgh(dot)pa(dot)us>, <kleptog(at)svana(dot)org>
Subject: Re: limiting hint bit I/O
Date: 2011-01-17 01:41:53
Message-ID: 4D334A010200002500039688@gw.wicourts.gov
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Robert Haas wrote:

> I think you may be confused about what the patch does - currently,
> pages with hint bit changes are considered dirty, period.
> Therefore, they are written whenever any other dirty page would be
> written: by the background writer cleaning scan, at checkpoints,
> and when a backend must write a dirty buffer before reallocating it
> to hold a different page. The patch keeps the first of these and
> changes the second two

No, I understood that. I'm just concerned that if you eliminate the
other two, we may be recomputing visibility based on clog often
enough to kill performance.

In other words, I'm asking that you show that the other two methods
aren't really needed for decent overall performance.

-Kevin

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