From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755458Ab3BVDdI (ORCPT ); Thu, 21 Feb 2013 22:33:08 -0500 Received: from mga01.intel.com ([192.55.52.88]:22874 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755117Ab3BVDdE (ORCPT ); Thu, 21 Feb 2013 22:33:04 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,713,1355126400"; d="scan'208";a="290422605" Message-ID: <5126E705.3040308@intel.com> Date: Fri, 22 Feb 2013 11:33:25 +0800 From: Alex Shi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120912 Thunderbird/15.0.1 MIME-Version: 1.0 To: Michael Wang CC: Peter Zijlstra , LKML , Ingo Molnar , Paul Turner , Mike Galbraith , Andrew Morton , Ram Pai , "Nikunj A. Dadhania" , Namhyung Kim Subject: Re: [RFC PATCH v3 1/3] sched: schedule balance map foundation References: <51079178.3070002@linux.vnet.ibm.com> <510791B2.6090506@linux.vnet.ibm.com> <1361366720.10155.25.camel@laptop> <5125A966.6040601@linux.vnet.ibm.com> <1361446661.26780.15.camel@laptop> <5126DD98.7030202@linux.vnet.ibm.com> In-Reply-To: <5126DD98.7030202@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/22/2013 10:53 AM, Michael Wang wrote: >> > >>> >> And the final cost is 3000 int and 1030000 pointer, and some padding, >>> >> but won't bigger than 10M, not a big deal for a system with 1000 cpu >>> >> too. >> > >> > Maybe, but quadric stuff should be frowned upon at all times, these >> > things tend to explode when you least expect it. >> > >> > For instance, IIRC the biggest single image system SGI booted had 16k >> > cpus in there, that ends up at something like 14+14+3=31 aka as 2G of >> > storage just for your lookup -- that seems somewhat preposterous. > Honestly, if I'm a admin who own 16k cpus system (I could not even image > how many memory it could have...), I really prefer to exchange 2G memory > to gain some performance. > > I see your point here, the cost of space will grow exponentially, but > the memory of system will also grow, and according to my understanding , > it's faster. Why not seek other way to change O(n^2) to O(n)? Access 2G memory is unbelievable performance cost. There are too many jokes on the short-sight of compute scalability, like Gates' 64K memory in 2000. -- Thanks Alex