From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759545AbXKTMLc (ORCPT ); Tue, 20 Nov 2007 07:11:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756802AbXKTMLL (ORCPT ); Tue, 20 Nov 2007 07:11:11 -0500 Received: from ns2.suse.de ([195.135.220.15]:32943 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756312AbXKTMLK (ORCPT ); Tue, 20 Nov 2007 07:11:10 -0500 From: Andi Kleen To: Nick Piggin Subject: Re: [rfc 08/45] cpu alloc: x86 support Date: Tue, 20 Nov 2007 13:05:24 +0100 User-Agent: KMail/1.9.1 Cc: Christoph Lameter , "H. Peter Anvin" , akpm@linux-foundation.org, travis@sgi.com, Mathieu Desnoyers , linux-kernel@vger.kernel.org References: <20071120011132.143632442@sgi.com> <200711201459.12841.nickpiggin@yahoo.com.au> In-Reply-To: <200711201459.12841.nickpiggin@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200711201305.24574.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > 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%?) > > Small socket count systems are going to increasingly be NUMA in future. > If CONFIG_NUMA hurts performance by that much on those systems, then the > kernel is broken IMO. Not sure where that number came from. In my tests some time ago NUMA overhead on SMP was minimal. This was admittedly with old 2.4 kernels. There have been some doubts about some of the newer NUMA features added; in particular about NUMA slab; don't think there was much trouble with anything else -- in fact the trouble was that it apparently sometimes made moderate NUMA factor NUMA systems slower too. But I assume SLUB will address this anyways. -Andi