Date: Tue, 2 Aug 2005 12:25:50 -0500
From: "Jim C. Nasby" <decibel@decibel.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Tobias Brox <tobias@nordicbet.com>,
	pgsql-performance@postgresql.org
Subject: Re: "nice"/low priority Query
Message-ID: <20050802172550.GZ60019@decibel.org>
References: <20050802160434.GD9278@tobias.lan>
 <11484.1122999570@sss.pgh.pa.us>
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On Tue, Aug 02, 2005 at 12:19:30PM -0400, Tom Lane wrote:
> Tobias Brox <tobias@nordicbet.com> writes:
> > Is there any ways to give postgresql a hint that a
> > particular SQL call should be run at lower priority?  Since every db
> > connection has a pid, I can manually run "renice" to scheduele it by the OS
> > - but of course I can't do it manually all the time.
> 
> And it won't help you anyway, because renice only affects CPU priority
> not I/O scheduling ... which, by your description, is the real problem.

Actually, from what I've read 4.2BSD actually took priority into account
when scheduling I/O. I don't know if this behavior is still present in
FreeBSD or the like, though. So depending on the OS, priority could play
a role in determining I/O scheduling.
-- 
Jim C. Nasby, Database Consultant               decibel@decibel.org 
Give your computer some brain candy! www.distributed.net Team #1828

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