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From: William Yu <wyu@talisys.com>
To: pgsql-performance@postgresql.org
Subject: Re: Caching by Postgres
Date: Wed, 24 Aug 2005 11:54:42 -0700
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In-Reply-To: <430C7448.7030103@sun.com>
References: <20050823171045.12112.qmail@web51309.mail.yahoo.com>
	<20050823124323.710a9dd3.frank@wiles.org>
	<430B6DE3.6040109@sun.com>
	<deg68k$16gh$1@news.hub.org>
	<430C7448.7030103@sun.com>

Donald Courtney wrote:
> I built postgreSQL 8.1 64K bit on solaris 10 a few months ago
> and side by side with the 32 bit postgreSQL build saw no improvement. In 
> fact the 64 bit result was slightly lower.

I'm not surprised 32-bit binaries running on a 64-bit OS would be faster 
than 64-bit/64-bit. 64-bit isn't some magical wand you wave and it's all 
ok. Programs compiled as 64-bit will only run faster if (1) you need 
64-bit address space and you've been using ugly hacks like PAE to get 
access to memory > 2GB or (2) you need native 64-bit data types and 
you've been using ugly hacks to piece 32-bit ints together (example, 
encryption/compression). In most cases, 64-bit will run slightly slower 
due to extra overhead of using larger datatypes.

Since PostgreSQL hands off the majority of memory management/data 
caching to the OS, only the OS needs to be 64-bit to reap the benefits 
of better memory management. Since Postgres *ALREADY* reaps the 64-bit 
benefit, I'm not sure how the argument moving caching/mm/fs into 
Postgres would apply. Yes there's the point about possibly implementing 
better/smarter/more appropriate caching algorithms but that has nothing 
to do with 64-bit.

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