Date: Mon, 03 Apr 2000 01:13:35 -0700 From: Doug Barton <Doug@gorean.org> To: nino@inode.at Cc: David Greenman <dg@root.com>, questions@freebsd.org Subject: Re: tuning the vm system / disk cache Message-ID: <38E852AF.30CCEEE0@gorean.org> References: <20000403025556.S31173@TK147108.telekabel.at> <200004030209.TAA07259@implode.root.com> <20000403044319.V31173@TK147108.telekabel.at>
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"Marinos J . Yannikos" wrote: > > 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. This sounds like a textbook use of a memory filesystem. I've never set one up, but http://www.freebsd.org/handbook/disks-virtual.html looks promising. :) Good luck, Doug -- "So, the cows were part of a dream that dreamed itself into existence? Is that possible?" asked the student incredulously. The master simply replied, "Mu." To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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