From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from casper.infradead.org (casper.infradead.org [85.118.1.10]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 1ABA5B6FC0 for ; Thu, 10 Mar 2011 00:34:08 +1100 (EST) Subject: Re: [BUG] rebuild_sched_domains considered dangerous From: Peter Zijlstra To: Martin Schwidefsky In-Reply-To: <20110309143152.3cc6c191@mschwide.boeblingen.de.ibm.com> References: <1299639487.22236.256.camel@pasglop> <1299665998.2308.2753.camel@twins> <1299670429.2308.2834.camel@twins> <20110309141548.722e4f56@mschwide.boeblingen.de.ibm.com> <1299676769.2308.2944.camel@twins> <20110309143152.3cc6c191@mschwide.boeblingen.de.ibm.com> Content-Type: text/plain; charset="UTF-8" Date: Wed, 09 Mar 2011 14:33:56 +0100 Message-ID: <1299677636.2308.2960.camel@twins> Mime-Version: 1.0 Cc: linuxppc-dev , "linux-kernel@vger.kernel.org" , Jesse Larrew List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2011-03-09 at 14:31 +0100, Martin Schwidefsky wrote: > > But if you don't also update the cpu->node memory mappings (which I > > think it near impossible) what good is it to change the scheduler > > topology? >=20 > The memory for the different LPARs is striped over all nodes (or books as= we > call them). We heavily rely on the large shared cache between the books t= o hide > the different memory access latencies.=20 Right, so effectively you don't have NUMA due to that striping. So why then change the CPU topology? Simply create a topology without NUMA and keep it static, that accurately reflects the memory topology.