| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com>, 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: | 2011-02-07 15:48:41 |
| Message-ID: | 201102071548.p17FmfB14418@momjian.us |
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| Lists: | pgsql-hackers |
Robert Haas wrote:
> On Sat, Feb 5, 2011 at 4:31 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> > Uh, in this C comment:
> >
> > + ? ? ? ?* or not we want to take the time to write it. ?We allow up to 5% of
> > + ? ? ? ?* otherwise-not-dirty pages to be written due to hint bit changes,
> >
> > 5% of what? ?5% of all buffers? ?5% of all hint-bit-dirty ones? ?Can you
> > clarify this in the patch?
>
> 5% of buffers that are hint-bit-dirty but not otherwise dirty. ISTM
> that's exactly what the comment you just quoted says on its face, but
> I'm open to some other wording you want to propose.
How about:
otherwise-not-dirty -> only-hint-bit-dirty
So 95% of your hint bit modificates are discarded if the pages is not
otherwise dirtied? That seems pretty radical.
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
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