Re: Free WAL caches on switching segments

From: ITAGAKI Takahiro <itagaki(dot)takahiro(at)lab(dot)ntt(dot)co(dot)jp>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: Free WAL caches on switching segments
Date: 2006-02-13 02:43:17
Message-ID: 20060213104414.49B2.ITAGAKI.TAKAHIRO@lab.ntt.co.jp
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Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> wrote:

> I looked this over and I am unsure what this does for us that isn't
> already accomplished using the wal_sync_method settings. See xlog.c for
> a description of O_DIRECT and when it is used.

I proposed it to supplement the cache control. There are some OSes that
supports posix_fadvise but not O_DIRECT, for example, NetBSD 4.0
(http://www.netbsd.org/Changes/changes-4.0.html).

---
ITAGAKI Takahiro
NTT Cyber Space Laboratories

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