Re: Script to compute random page cost

I got somewhat different:

$ ./randcost /usr/local/pgsql/data
Collecting sizing information ...
Running random access timing test ...
Running sequential access timing test ...
Running null loop timing test ...
random test: 13
sequential test: 15
null timing test: 11

random_page_cost = 0.500000

Chris

> -----Original Message-----
> From: pgsql-hackers-owner(at)postgresql(dot)org
> [mailto:pgsql-hackers-owner(at)postgresql(dot)org]On Behalf Of Bruce Momjian
> Sent: Tuesday, 10 September 2002 2:02 PM
> To: Curt Sampson
> Cc: Tom Lane; nickf(at)ontko(dot)com; PostgreSQL-development; Ray Ontko
> Subject: Re: [HACKERS] Script to compute random page cost
>
>
> OK, I have a better version at:
>
> ftp://candle.pha.pa.us/pub/postgresql/randcost
>
> I have added a null loop which does a dd on a single file without
> reading any data, and by netting that loop out of the total computation
> and increasing the number of tests, I have gotten the following results
> for three runs:
>
> random test: 36
> sequential test: 33
> null timing test: 27
>
> random_page_cost = 1.500000
>
>
> random test: 38
> sequential test: 32
> null timing test: 27
>
> random_page_cost = 2.200000
>
>
> random test: 40
> sequential test: 31
> null timing test: 27
>
> random_page_cost = 3.250000
>
> Interesting that random time is increasing, while the others were
> stable. I think this may have to do with other system activity at the
> time of the test. I will run it some more tomorrow but clearly we are
> seeing reasonable numbers now.
>
> --
> Bruce Momjian | http://candle.pha.pa.us
> pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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