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Re: Solaris shared_buffers anomaly?

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Cc: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>, Mischa Sandberg <mischa(at)ca(dot)sophos(dot)com>
Subject: Re: Solaris shared_buffers anomaly?
Date: 2006-06-14 21:25:04
Message-ID: 200606141425.04600.josh@agliodbs.com (view raw or flat)
Thread:
Lists: pgsql-performance
Folks,

First off, you'll be glad to know that I've persuaded two of the Sun 
performance engineers to join this list soon.   So you should be able to 
get more difinitive answers to these questions.

Second, 7.4 still did linear scanning of shared_buffers as part of LRU and 
for other activities.   I don't know how that would cause swapping, but it 
certainly could cause dramatic slowdowns (like 2-5x) if you overallocated 
shared_buffers.   

Possibly this is also triggering a bug in Solaris 2.6.   2.6 is pretty 
darned old (1997); maybe you should upgrade?   We're testing with s_b set 
to 300,000 on Solaris 10 (Niagara) so this is obviously not a current 
Solaris issue.

-- 
--Josh

Josh Berkus
PostgreSQL @ Sun
San Francisco

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