X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 95FB0D79B8 for ; Wed, 24 Aug 2005 18:09:19 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 94582-07 for ; Wed, 24 Aug 2005 21:09:16 +0000 (GMT) Received: from vms042pub.verizon.net (vms042pub.verizon.net [206.46.252.42]) by svr1.postgresql.org (Postfix) with ESMTP id C551AD78C3 for ; Wed, 24 Aug 2005 18:09:12 -0300 (ADT) Received: from osgiliath.mathom.us ([151.200.14.55]) by vms042.mailsrvcs.net (Sun Java System Messaging Server 6.2 HotFix 0.04 (built Dec 24 2004)) with ESMTPA id <0ILQ009HTW3950E1@vms042.mailsrvcs.net> for pgsql-performance@postgresql.org; Wed, 24 Aug 2005 16:09:11 -0500 (CDT) Received: from localhost (localhost [127.0.0.1]) by osgiliath.mathom.us (Postfix) with ESMTP id 861F060263C for ; Wed, 24 Aug 2005 17:09:09 -0400 (EDT) Received: from osgiliath.mathom.us ([127.0.0.1]) by localhost (osgiliath [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 29379-02-8 for ; Wed, 24 Aug 2005 17:09:09 -0400 (EDT) Received: by osgiliath.mathom.us (Postfix, from userid 1000) id 6A627602638; Wed, 24 Aug 2005 17:09:09 -0400 (EDT) Date: Wed, 24 Aug 2005 17:09:09 -0400 From: Michael Stone Subject: Re: Caching by Postgres In-reply-to: <20050824193441.GA13772@mark.mielke.cc> To: pgsql-performance@postgresql.org Mail-Followup-To: pgsql-performance@postgresql.org Message-id: <20050824210909.GN8667@mathom.us> MIME-version: 1.0 Content-type: text/plain; charset=us-ascii; format=flowed Content-disposition: inline X-Pgp-Fingerprint: 53 FF 38 00 E7 DD 0A 9C 84 52 84 C5 EE DF 7C 88 X-Virus-Scanned: by amavisd-new-20030616-p10 (Debian) at mathom.us References: <20050823171045.12112.qmail@web51309.mail.yahoo.com> <20050823124323.710a9dd3.frank@wiles.org> <430B6DE3.6040109@sun.com> <430C7448.7030103@sun.com> <20050824173055.GA11788@mark.mielke.cc> <430CC0AD.5040400@rentec.com> <20050824193441.GA13772@mark.mielke.cc> User-Agent: Mutt/1.5.10i X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.041 required=5 tests=[AWL=-0.009, FORGED_RCVD_HELO=0.05] X-Spam-Level: X-Archive-Number: 200508/408 X-Sequence-Number: 14155 On Wed, Aug 24, 2005 at 03:34:41PM -0400, mark@mark.mielke.cc wrote: >It isn't an urban myth that 64-bit math on a 64-bit processor is >faster, at least if done using registers. It definately is faster. >It may be an urban myth, though, that most applications perform >a sufficient amount of 64-bit arithmetic to warrant the upgrade. The mjor problem is that the definition of "64bit processor" is fuzzy. The major slowdown of "64bitness" is the necessity of carting around 64 bit pointers. It's not, however, necessary to do 64bit pointers to get 64bit registers & fast 64 bit ops. E.g., sgi has "n32" & "n64" abi's which can access exactly the same instruction set & registers, the difference between them is the size of pointers and whether a "long" is the same as a "long long". Any discussion of "64 bit processors" is doomed from the start because people tend to start making implementation assumptions on top of an already vague concept. Current & future discussions are tinged by the fact that amd64 *doubles* the number of registers in 64 bit mode, potentially providing a major speedup--but one that doesn't really have anything to do with being "64bit". Pretty much any discussion of 64 bit mode really needs to be a discussion of a particular abi on a particular processor; talking about "64 bit processors" abstractly is a waste of time. Mike Stone