From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758519AbXKTCOW (ORCPT ); Mon, 19 Nov 2007 21:14:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760893AbXKTCCN (ORCPT ); Mon, 19 Nov 2007 21:02:13 -0500 Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:39336 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1759816AbXKTCCL (ORCPT ); Mon, 19 Nov 2007 21:02:11 -0500 Date: Mon, 19 Nov 2007 18:02:11 -0800 (PST) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: "H. Peter Anvin" cc: ak@suse.de, akpm@linux-foundation.org, travis@sgi.com, Mathieu Desnoyers , linux-kernel@vger.kernel.org Subject: Re: [rfc 08/45] cpu alloc: x86 support In-Reply-To: <474239CA.20403@zytor.com> Message-ID: References: <20071120011132.143632442@sgi.com> <20071120011333.619991903@sgi.com> <474239CA.20403@zytor.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 19 Nov 2007, H. Peter Anvin wrote: > You're making the assumption here that NUMA = large number of CPUs. This > assumption is flat-out wrong. Well maybe. Usually one gets to NUMA because the hardware gets too big to be handleed the UMA way. > On x86-64, most two-socket systems are still NUMA, and I would expect that > most distro kernels probably compile in NUMA. However, > burning megabytes of memory on a two-socket dual-core system when we're > talking about tens of kilobytes used would be more than a wee bit insane. Yeah yea but the latencies are minimal making the NUMA logic too expensive for most loads ... If you put a NUMA kernel onto those then performance drops (I think someone measures 15-30%?)