Re: Initial prefetch performance testing - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Initial prefetch performance testing
Date
Msg-id 27545.1222177797@sss.pgh.pa.us
Whole thread Raw
In response to Re: Initial prefetch performance testing  (Gregory Stark <stark@enterprisedb.com>)
List pgsql-hackers
Gregory Stark <stark@enterprisedb.com> writes:
> Perhaps access paths which expect to be able to prefetch most of their
> accesses should use random_page_cost / effective_spindle_count for their i/o
> costs?

> But then if people don't set random_page_cost high enough they could easily
> find themselves with random fetches being costed as less expensive than
> sequential fetches. And I have a feeling it'll be a hard sell to get people to
> set random_page_cost in the double digits let alone triple digits.

Well, we could use something likeMax(random_page_cost / effective_spindle_count, seq_page_cost)
to ensure the result remains somewhat sane.
        regards, tom lane


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