Re: Dirty Buffer Writing [was Proposed LogWriter Scheme]

From: Greg Copeland <greg(at)CopelandConsulting(dot)Net>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Curtis Faith <curtis(at)galtair(dot)com>, Pgsql-Hackers <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: Dirty Buffer Writing [was Proposed LogWriter Scheme]
Date: 2002-10-07 21:28:08
Message-ID: 1034026089.26051.253.camel@mouse.copelandconsulting.net
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On Mon, 2002-10-07 at 15:28, Bruce Momjian wrote:
> This is the trickle syncer. It prevents bursts of disk activity every
> 30 seconds. It is for non-fsync writes, of course, and I assume if the
> kernel buffers get low, it starts to flush faster.

Doesn't this also increase the likelihood that people will be running in
a buffer-poor environment more frequently that I previously asserted,
especially in very heavily I/O bound systems? Unless I'm mistaken, that
opens the door for a general case of why an aio implementation should be
looked into.

Also, on a side note, IIRC, linux kernel 2.5.x has a new priority
elevator which is said to be MUCH better as saturating disks than ever
before. Once 2.6 (or whatever it's number will be) is released, it may
not be as much of a problem as it seems to be for FreeBSD (I think
that's the one you're using).

Greg

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