Date: Sun, 02 Apr 2000 19:55:07 -0700 From: David Greenman <dg@root.com> To: nino@inode.at Cc: questions@freebsd.org Subject: Re: tuning the vm system / disk cache Message-ID: <200004030255.TAA07463@implode.root.com> In-Reply-To: Your message of "Mon, 03 Apr 2000 04:43:19 %2B0200." <20000403044319.V31173@TK147108.telekabel.at>
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>On Sun, Apr 02, 2000 at 07:09:52PM -0700, David Greenman wrote: >> I'm sure the system is already caching the entire file - evidence of this >> is the 438M of free memory, which the system would directly allocate from in >> order to cache the file. The only way I can explain the disk I/O is that there >> must be some writes taking place for some reason. > >You're right (of course). I checked Postgres' data directory and, >surprisingly, it writes temporary files for every query. Their filenames >begin with "pg_sorttemp", so the GROUP BY clause seems to be the culprit. > >Shouldn't it be possible to get rid of those disk accesses somehow? >These are very short-lived files, softupdates are enabled. -current/4.x-stable might behave better with the recent changes to reduce async write-behind. It all depends on the nature of the file writes and size of the file. This area is Matt Dillon's recent domain, so you may wish to discuss this with him. -DG David Greenman Co-founder/Principal Architect, The FreeBSD Project - http://www.freebsd.org Creator of high-performance Internet servers - http://www.terasolutions.com Pave the road of life with opportunities. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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