Re: limiting hint bit I/O

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: <josh(at)agliodbs(dot)com>,<robertmhaas(at)gmail(dot)com>
Cc: <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: 2011-01-16 22:37:16
Message-ID: 4D331EBC0200002500039680@gw.wicourts.gov
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Robert Haas wrote:

> a quick-and-dirty attempt to limit the amount of I/O caused by hint
> bits. I'm still very interested in knowing what people think about
> that.

I found the elimination of the response-time spike promising. I
don't think I've seen enough data yet to feel comfortable endorsing
it, though. I guess the question in my head is: how much of the
lingering performance hit was due to having to go to clog and how
much was due to competition with the deferred writes? If much of it
is due to repeated recalculation of visibility based on clog info, I
think there would need to be some way to limit how many times that
happened before the hint bits were saved.

-Kevin

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