Re: [HACKERS] fsync method checking

From: Kurt Roeckx <Q(at)ping(dot)be>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Mark Kirkwood <markir(at)paradise(dot)net(dot)nz>, pgsql-performance(at)postgresql(dot)org, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] fsync method checking
Date: 2004-03-18 20:03:59
Message-ID: 20040318200359.GA8330@ping.be
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On Thu, Mar 18, 2004 at 02:22:10PM -0500, Bruce Momjian wrote:
>
> OK, what better test do you suggest? Right now, there has been no
> testing of these.

I suggest you start by doing atleast preallocating a 16 MB file
and do the tests on that, to atleast be somewhat simular to what
WAL does.

I have no idea what the access pattern is for normal WAL
operations or how many times it gets synched. Does it only do
f(data)sync() at commit time, or for every block it writes?

I think if you write more data you'll see more differences
between O_(D)SYNC and f(data)sync().

I guess it can depend on if you have lots of small transactions,
or more big ones.

Atleast try to make something that covers different access
patterns.

Kurt

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