Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762071AbZJJSL3 (ORCPT ); Sat, 10 Oct 2009 14:11:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762060AbZJJSL2 (ORCPT ); Sat, 10 Oct 2009 14:11:28 -0400 Received: from lennier.cc.vt.edu ([198.82.162.213]:41867 "EHLO lennier.cc.vt.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762043AbZJJSL2 (ORCPT ); Sat, 10 Oct 2009 14:11:28 -0400 X-Mailer: exmh version 2.7.2 01/07/2005 with nmh-1.2 To: Jeff Chua Cc: Linus Torvalds , Tomasz Chmielewski , Daniel J Blueman , Byron Stanoszek , Dave Hansen , Hugh Dickins , Linux Kernel , Andrew Morton Subject: Re: 2.6.32-rc3: low mem - only 378MB on x86_32 with 64GB. Why? In-Reply-To: Your message of "Sat, 10 Oct 2009 00:28:42 +0800." From: Valdis.Kletnieks@vt.edu References: Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1255198236_250202P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Sat, 10 Oct 2009 14:10:36 -0400 Message-ID: <32059.1255198236@turing-police.cc.vt.edu> X-Mirapoint-Received-SPF: 128.173.38.202 turing-police.cc.vt.edu Valdis.Kletnieks@vt.edu 2 pass X-Mirapoint-IP-Reputation: reputation=neutral-1, source=Fixed, refid=n/a, actions=MAILHURDLE SPF TAG X-Junkmail-Info: (0) X-Junkmail-Status: score=10/50, host=steiner.cc.vt.edu X-Junkmail-SD-Raw: score=unknown, refid=str=0001.0A020208.4AD0CE1E.0028,ss=1,fgs=0, ip=0.0.0.0, so=2009-07-29 21:33:33, dmn=2009-09-10 00:05:08, mode=multiengine X-Junkmail-IWF: false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1444 Lines: 37 --==_Exmh_1255198236_250202P Content-Type: text/plain; charset=us-ascii On Sat, 10 Oct 2009 00:28:42 +0800, Jeff Chua said: > From all the reading I've read about how slow 64-bit was, after doing all > the lean and mean compiling, 64-bit is definitely the way to go! Fast and > worth every bit switching to 64-bit! Now I can go for 128GB ram. When the MIPS, PowerPC, and Sparc architectures went from 32 to 64 bits, they *did* take a bit of a performance hit because it basically doubled the memory bandwidth usage. However, they all had a reasonably large number of registers in 32-bit mode. When the x86 went 64-bit, the register pressure relief from the additional registers usually more then outweighs the additional memory bandwidth (basically, if you're spending twice as much time on each load/store, but only doing it 40% as often, you come out ahead...) --==_Exmh_1255198236_250202P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Exmh version 2.5 07/13/2001 iD8DBQFK0M4ccC3lWbTT17ARAlReAJ9Uc47tfas43Q8Af6xB2GuCY+8RGgCfXXuI Gsb9UdbOiDqN3xeNDCExOVc= =2Md7 -----END PGP SIGNATURE----- --==_Exmh_1255198236_250202P-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/