Re: [PERFORM] [PATCHES] ARC Memory Usage analysis

Josh Berkus <josh@agliodbs.com>

From: Josh Berkus <josh@agliodbs.com>
To: pgsql-hackers@postgresql.org
Cc: Thomas F.O'Connell <tfo@sitening.com>, Simon Riggs <simon@2ndquadrant.com>, PgSQL - Performance <pgsql-performance@postgresql.org>
Date: 2004-10-27T00:39:59Z
Lists: pgsql-hackers, pgsql-performance
Thomas,

> As a result, I was intending to inflate the value of
> effective_cache_size to closer to the amount of unused RAM on some of
> the machines I admin (once I've verified that they all have a unified
> buffer cache). Is that correct?

Currently, yes.  Right now, e_c_s is used just to inform the planner and make 
index vs. table scan and join order decisions.

The problem which Simon is bringing up is part of a discussion about doing 
*more* with the information supplied by e_c_s.    He points out that it's not 
really related to the *real* probability of any particular table being 
cached.   At least, if I'm reading him right.

-- 
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco