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Re: Disabling bgwriter on my notebook

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Michael Paesold" <mpaesold(at)gmx(dot)at>
Cc: pgsql-hackers(at)postgresql(dot)org, Jan Wieck <JanWieck(at)Yahoo(dot)com>
Subject: Re: Disabling bgwriter on my notebook
Date: 2004-09-17 20:14:32
Message-ID: 24295.1095452072@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
"Michael Paesold" <mpaesold(at)gmx(dot)at> writes:
> pgwriter is keeping my disks busy and disturbs me :-(. The more I like
> pgwriter for a production system, the less I like it on my desktop during
> developement.
> So I thought I would just be able to disable this, but that seems not the
> case.

You can't turn off the bgwriter process entirely anymore, because we
rely on it for checkpoints.  However I suppose there's no solid reason
not to allow bgwriter_delay to be set as high as checkpoint_timeout,
which would accomplish your goal of not spinning up the laptop disk very
often.

This reminds me of another issue I'd been meaning to bring up, which is
whether the default bgwriter settings are reasonable:

> #bgwriter_delay = 200  # 10-5000 milliseconds
> #bgwriter_percent = 1  # 1-100% of dirty buffers
> #bgwriter_maxpages = 100 # 1-1000 buffers max at once

ISTM that writing only 1% of dirty buffers per cycle isn't going to go
very far in terms of keeping the freelist clean.  I was wondering if the
default on that shouldn't be higher.  If 1% *is* a reasonable setting,
then don't we need finer granularity --- maybe the setting should be in
tenths of a percent?  Having the default right up against the end of the
possible range doesn't sound right.

Jan, you're probably the only one who's done any serious testing of
alternatives for this --- what do you think?

			regards, tom lane

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