From: Gregory Stark <stark@enterprisedb.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: ITAGAKI Takahiro <itagaki.takahiro@oss.ntt.co.jp>
Cc: Postgres <pgsql-hackers@postgresql.org>
Subject: Re: posix_fadvise v22
Date: Mon, 12 Jan 2009 01:55:56 -0500
Message-ID: <87mydxm2rn.fsf@oxford.xeocode.com> (raw)
In-Reply-To: <13517.1231737582@sss.pgh.pa.us>
References: <FDDBA24E-FF4D-4654-BA75-692B3BA71B97@enterprisedb.com>
<8347.1229012970@sss.pgh.pa.us>
<4136ffa0812110911x4914a951o6ca502879e3dede7@mail.gmail.com>
<87k5a6tmy7.fsf@oxford.xeocode.com>
<603c8f070901011230t1afa6644racb715b975078054@mail.gmail.com>
<10658.1230843315@sss.pgh.pa.us>
<603c8f070901011843p121e40afu35c4a7bdc51c051c@mail.gmail.com>
<13517.1231737582@sss.pgh.pa.us>
Tom Lane <tgl@sss.pgh.pa.us> writes:
> "Robert Haas" <robertmhaas@gmail.com> writes:
>> OK, here's an update of Greg's patch with the runtime configure test
>> ripped out, some minor documentation tweaks, and a few unnecessary
>> whitespace diff hunks quashed. I think this is about ready for
>> committer review.
>
> I've applied most of this, with a couple of notable revisions:
>
> 1. The runtime check on whether posix_fadvise works is really gone.
> We'll see whether we need to put anything back, but I think our first
> try should be under the assumption that it works. (BTW, I was wrong
> in my earlier claim that the buildfarm wouldn't exercise posix_fadvise
> by default --- the patch defaults to io_concurrency = 1 if fadvise
> is available, so it will try to prefetch one page ahead.)
>
> 2. I fixed it so that setting effective_io_concurrency to zero disables
> prefetching altogether; there was no way to do that in the patch as
> submitted.
Hm. the original intent was that effective_io_concurrency 1 meant no
prefetching because there was only one drive.
I wonder if that worked earlier and got lost along the way or if I always had
this wrong.
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's 24x7 Postgres support!
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To: pgsql-hackers@postgresql.org
Cc: stark@enterprisedb.com, tgl@sss.pgh.pa.us, robertmhaas@gmail.com, itagaki.takahiro@oss.ntt.co.jp
Subject: Re: posix_fadvise v22
In-Reply-To: <87mydxm2rn.fsf@oxford.xeocode.com>
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