Received: from localhost (maia-3.hub.org [200.46.204.184]) by postgresql.org (Postfix) with ESMTP id A63B69F9F46 for ; Mon, 11 Dec 2006 13:34:51 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.184]) (amavisd-new, port 10024) with ESMTP id 02189-04 for ; Mon, 11 Dec 2006 13:34:24 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from vms040pub.verizon.net (vms040pub.verizon.net [206.46.252.40]) by postgresql.org (Postfix) with ESMTP id 0B4339F9F49 for ; Mon, 11 Dec 2006 13:34:24 -0400 (AST) Received: from osgiliath.mathom.us ([71.246.251.8]) by vms040.mailsrvcs.net (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPA id <0JA400GW4E080N00@vms040.mailsrvcs.net> for pgsql-performance@postgresql.org; Mon, 11 Dec 2006 11:31:58 -0600 (CST) Received: from localhost (localhost [127.0.0.1]) by osgiliath.mathom.us (Postfix) with ESMTP id B2A0470ABD for ; Mon, 11 Dec 2006 12:31:09 -0500 (EST) Received: from osgiliath.mathom.us ([127.0.0.1]) by localhost (osgiliath.home.mathom.us [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 2FwuEnaBr0a8 for ; Mon, 11 Dec 2006 12:31:08 -0500 (EST) Received: by osgiliath.mathom.us (Postfix, from userid 1000) id 8397F70ABE; Mon, 11 Dec 2006 12:31:08 -0500 (EST) Date: Mon, 11 Dec 2006 12:31:08 -0500 From: Michael Stone Subject: Re: New to PostgreSQL, performance considerations In-reply-to: To: pgsql-performance@postgresql.org Mail-followup-to: pgsql-performance@postgresql.org Message-id: <20061211173105.GH16692@mathom.us> MIME-version: 1.0 Content-type: text/plain; charset=us-ascii; format=flowed Content-disposition: inline X-Virus-Scanned: Debian amavisd-new at mathom.us X-Pgp-Fingerprint: 53 FF 38 00 E7 DD 0A 9C 84 52 84 C5 EE DF 7C 88 References: <8a0c7af10612101141n2c7727c3r2f92345753960808@mail.gmail.com> <430d92a20612101336r3de8862coe618277fccb4006a@mail.gmail.com> <8a0c7af10612101702i49b5a533v4a2300d90d9dae6b@mail.gmail.com> <20061211021847.GE16692@mathom.us> <8a0c7af10612110305u305124b2v3d63491b5f57a86b@mail.gmail.com> <87u002mv49.fsf@wolfe.cbbrowne.com> <8a0c7af10612110531sbb019ck259fb16d131fdb50@mail.gmail.com> <60psaq5t94.fsf@dba2.int.libertyrms.com> User-Agent: Mutt/1.5.13 (2006-08-11) X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200612/248 X-Sequence-Number: 22304 On Mon, Dec 11, 2006 at 12:15:51PM -0500, Ron wrote: >I'd say the fairest attitude is to do everything we can to support >having the proper experiments done w/o presuming the results. Who's presuming results?[1] It is fair to say that making extraordinary claims without any evidence should be discouraged. It's also fair to say that if there are specific things that need cpu-specific tuning they'll be fairly limited critical areas (e.g., locks) which would probably be better implemented with a hand-tuned code and runtime cpu detection than by magical mystical compiler invocations. Mike Stone [1] I will say that I have never seen a realistic benchmark of general code where the compiler flags made a statistically significant difference in the runtime. There are some particularly cpu-intensive codes, like some science simulations or encoding routines where they matter, but that's not the norm--and many of those algorithms already have hand-tuned versions which will outperform autogenerated code. You'd think that with all the talk that the users of certain OS's generate about CFLAG settings, there'd be some well-published numbers backing up the hype. At any rate if there were numbers to back the claim then I think they could certainly be considered without prejudice.