User-Agent: Microsoft-Entourage/11.2.3.060209
Date: Mon, 12 Jun 2006 19:57:32 -0700
Subject: Re: 64-bit vs 32-bit performance ... backwards?
From: "Luke Lonergan" <llonergan@greenplum.com>
To: mark@mark.mielke.cc, "Anthony Presley" <anthony@resolution.com>,
	pgsql-performance@postgresql.org
Message-ID: <C0B377AC.26F41%llonergan@greenplum.com>
Thread-Topic: [PERFORM] 64-bit vs 32-bit performance ... backwards?
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In-Reply-To: <20060613021627.GA4682@mark.mielke.cc>
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Mark,

On 6/12/06 7:16 PM, "mark@mark.mielke.cc" <mark@mark.mielke.cc> wrote:

> I haven't. I'm meaning to take a look. Within registers, 64-bit should
> be equal speed to 32-bit. Outside the registers, it would make sense
> to only deal with the lower 32-bits where 32-bits is all that is
> required.

The short answer to all of this as shown in many lab tests by us and
elsewhere (see prior post):

- 64-bit pgsql on Opteron is generally faster than 32-bit, often by a large
amount (20%-30%) on queries that perform sorting, aggregation, etc.  It's
generally not slower.

- 64-bit pgsql on Xeon is generally slower than 32-bit by about 5%

So if you have Opterons and you want the best performance, run in 64-bit.
If you have Xeons, you would only run in 64-bit if you use more than 4GB of
memory.

- Luke