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Re: posix_fadvise v22

From: "Robert Haas" <robertmhaas(at)gmail(dot)com>
To: "Gregory Stark" <stark(at)enterprisedb(dot)com>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "ITAGAKI Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, Postgres <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: posix_fadvise v22
Date: 2009-01-01 20:30:26
Message-ID: 603c8f070901011230t1afa6644racb715b975078054@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
I tried this on my laptop running FC9, and because I forgot to run
autoconf, I got this error message when I tried to turn on
posix_fadvise.

rhaas=# set effective_io_concurrency to 3;
ERROR:  could not determine if this system has a working posix_fadvise
DETAIL:  Check configure.log produced by configure for more information

Am I correct in thinking that the only thing we're really checking for
here is whether a trivial posix_fadvise() call returns success?  If
so, is this test really worth doing?  It seems to me that since users
can always switch off the feature by leaving effective_io_concurrency
set to the default value of 1, there is not much value in having a
configure test that forcibly disables it.  If the user has a broken
posix_fadvise() and later fixes it, they shouldn't have to recompile
PostgreSQL to use this feature, especially in this day when the build
system and the run system are often different.  A user who somehow
ends up with RPMs that generate this error message will be utterly at
a loss as to what to do about it.

One minor nit: If we're going to keep this test, we should change the
detail string to say config.log rather than configure.log, as that is
the actual file name.

...Robert

On Thu, Dec 11, 2008 at 4:35 PM, Gregory Stark <stark(at)enterprisedb(dot)com> wrote:
> Here's the update
>
> I also skimmed through and cleaned a couple other things. There's *still* a
> function prototype which I don't see what header file to put it in, that's the
> one in port/posix_fadvise.c which contains one function with one caller, guc.c.
>
>
> --
>  Gregory Stark
>  EnterpriseDB          http://www.enterprisedb.com
>  Ask me about EnterpriseDB's 24x7 Postgres support!
>
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Subject: Re: posix_fadvise v22
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