Date: Wed, 24 Aug 2005 10:55:33 -0400
From: Stephen Frost <sfrost@snowman.net>
To: Donald Courtney <Donald.Courtney@sun.com>
Cc: William Yu <wyu@talisys.com>, pgsql-performance@postgresql.org
Subject: Re: Caching by Postgres
Message-ID: <20050824145533.GN6026@ns.snowman.net>
Mail-Followup-To: Donald Courtney <Donald.Courtney@sun.com>,
	William Yu <wyu@talisys.com>, pgsql-performance@postgresql.org
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	<20050823124323.710a9dd3.frank@wiles.org>
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* Donald Courtney (Donald.Courtney@sun.com) wrote:
> To be clear -
> 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.=20
> In fact the 64 bit result was slightly lower.

That makes some sense actually.  It really depends on what you're doing
alot of the time.  On a Sparc system you're not likely to get much of a
speed improvment by going to 64bit (unless, maybe, you're doing lots of
intensive 64bit math ops).  You'll have larger pointers and whatnot
though.

> I used  the *same 64 bit S10 OS* for both versions.  I think your
> experience makes sense since your change was from 32 to 64 bit Linux.

32bit to 64bit Linux on a Sparc platform really shouldn't affect
performance all that much (I'd expect it to be similar to 32bit to 64bit
under Solaris actually, at least in terms of the performance
difference).  32bit to 64bit Linux on an amd64 platform is another
matter entirely though, but not because of the number of bits involved.

Under amd64, 32bit is limited to 32bit on i386 which has a limited
number of registers and whatnot.  Under amd64/64bit you get more
registers (and I think some other niceities) which will improve
performance.  That's not a 32bit vs. 64bit thing, that's i386 vs. native
amd64.  It's really mainly an oddity of the platform.  On a mips system
I'd expect the same kind of performance difference between 32bit and
64bit as you'd see on a sparc platform.

	Enjoy,

		Stephen

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