Re: limiting hint bit I/O

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com>
Cc: Bruce Momjian <bruce(at)momjian(dot)us>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Merlin Moncure <mmoncure(at)gmail(dot)com>, Jim Nasby <jim(at)nasby(dot)net>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: limiting hint bit I/O
Date: 2011-02-06 00:35:43
Message-ID: AANLkTi=Ex3XKryfSD1Yqc3NYpHvmd_9+euhQ4e2=pZL1@mail.gmail.com
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On Sat, Feb 5, 2011 at 5:04 PM, Cédric Villemain
<cedric(dot)villemain(dot)debian(at)gmail(dot)com> wrote:
> Robert, I am unsure with the hint_bit_write_allowance counter. It
> looks a bit fragile because
> nothing prevent  hint_bit_write_allowance counter to increase a lot,
> so that is not 100 but X*100 next hint bit will be written. Isn't it ?

hint_bit_write_allowance can never be more than 100. The only things
we ever do are set it to exactly 100, and decrease it by 1 if it's
positive.

> Also, won't buffer_allocation_count hit INT limit ?

Sure, if the backend sticks around long enough, but it's no big deal
if it overflows.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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