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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: (view raw or whole 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

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.


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
>  Ask me about EnterpriseDB's 24x7 Postgres support!
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