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Re: Free WAL caches on switching segments

From: daveg <daveg(at)sonic(dot)net>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>,ITAGAKI Takahiro <itagaki(dot)takahiro(at)lab(dot)ntt(dot)co(dot)jp>,pgsql-patches(at)postgresql(dot)org
Subject: Re: Free WAL caches on switching segments
Date: 2006-02-13 22:50:36
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-patches
On Mon, Feb 13, 2006 at 02:59:43PM -0500, Bruce Momjian wrote:
> Tom Lane wrote:
> > Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > > Tom Lane wrote:
> > >> More to the point, the utility of the patch remains unproven.
> > >> We are not in the habit of adding OS dependencies on speculation.
> > 
> > > He ran tests, though it is speculation because non-caching is a pretty
> > > hard thing to find a benefit from except under low memory situations.
> > 
> > Well, the tests (a) didn't show any particularly good speedup, and
> > (b) were not on the platforms that this is speculated to be useful on
> > (ie, those without O_DIRECT).
> > 
> > I really don't think that an adequate case has been made for adding
> > a new OS dependency.
> Well, I think the patch should be applied, and the submitter does too,
> so unless I hear other votes, it is going in.

I vote no for whatever that is worth.  A "performance" change needs to
actually demonstrate improved performance.  If the change is really
desireable to clean up some messy code, then add it as a cleanup change
without the extra system calls. Otherwise it just adds one more bit of
mystery for future maintainers who may be decieved into thinking that posix
advise calls are important voodoo.


David Gould                      daveg(at)sonic(dot)net
If simplicity worked, the world would be overrun with insects.

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Subject: Re: Free WAL caches on switching segments
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