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Re: Postgresql 8.0 beta 1 - strange cpu usage statistics and slow vacuuming

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Shelby Cain <alyandon(at)yahoo(dot)com>
Cc: pgsql-general <pgsql-general(at)postgresql(dot)org>,pgsql-hackers-win32(at)postgresql(dot)org
Subject: Re: Postgresql 8.0 beta 1 - strange cpu usage statistics and slow vacuuming
Date: 2004-08-19 17:09:07
Message-ID: 324.1092935347@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-hackers-win32
Shelby Cain <alyandon(at)yahoo(dot)com> writes:
> I'm putting 8.0 through its paces and here are a few
> things I've noticed on the native win32 port running
> on my workstation (2.0g p4 w/256 megs of ram).

> Here is the output of "vacuum verbose item":

> DETAIL:  CPU -1.-1612s/-1.99u sec elapsed 1434.79 sec.
> ...
> CPU 1081264882.-821s/0.02u sec elapsed 1682.87 sec.

Hmm ... something broken about getrusage() on Windows?
CC'd to pgsql-hackers-win32 for comment.

> My other concern is the length of time that vacuum
> runs when cost based vacuuming is disabled.

Are you sure you had cost-based vac disabled?  I tried to reproduce
your experiment here.  I saw some degradation in vacuuming speed
but not nearly as large as you're reporting (85 vs 73 seconds),
and as far as I could tell it was still maxing out my disk.
But the behavior you're describing is exactly what I'd expect if
cost-based vac was on.

			regards, tom lane

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