| From: | Curt Sampson <cjs(at)cynic(dot)net> |
|---|---|
| To: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgreSQL(dot)org> |
| Subject: | Re: Script to compute random page cost |
| Date: | 2002-09-09 10:52:46 |
| Message-ID: | Pine.NEB.4.44.0209091944340.479-100000@angelic.cynic.net |
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| Thread: | |
| Lists: | pgsql-hackers |
On Mon, 9 Sep 2002, Bruce Momjian wrote:
> What do other people get for this value?
With your new script, with a 1.5 GHz Athlon, 512 MB RAM, and a nice fast
IBM 7200 RPM IDE disk, I get random_page_cost = 0.933333.
> One flaw in this test is that it randomly reads blocks from different
> files rather than randomly reading from the same file. Do people have a
> suggestion on how to correct this? Does it matter?
From my quick glance, it also does a lot of work work to read each
block, including forking off serveral other programs. This would tend to
push up the cost of a random read. You might want to look at modifying
the randread program (http://randread.sourceforge.net) to do what you
want....
cjs
--
Curt Sampson <cjs(at)cynic(dot)net> +81 90 7737 2974 http://www.netbsd.org
Don't you know, in this new Dark Age, we're all light. --XTC
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