From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422667AbVLOJg6 (ORCPT ); Thu, 15 Dec 2005 04:36:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422668AbVLOJg5 (ORCPT ); Thu, 15 Dec 2005 04:36:57 -0500 Received: from mx1.suse.de ([195.135.220.2]:7307 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S1422667AbVLOJg5 (ORCPT ); Thu, 15 Dec 2005 04:36:57 -0500 Date: Thu, 15 Dec 2005 10:36:45 +0100 From: Andi Kleen To: Eric Dumazet Cc: Ravikiran G Thirumalai , Andi Kleen , linux-kernel@vger.kernel.org, discuss@x86-64.org, Andrew Morton , dada1@cosmobay.com Subject: Re: [patch 3/3] x86_64: Node local pda take 2 -- node local pda allocation Message-ID: <20051215093645.GW23384@wotan.suse.de> References: <20051215023345.GB3787@localhost.localdomain> <20051215023748.GD3787@localhost.localdomain> <43A127D3.1070106@cosmosbay.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <43A127D3.1070106@cosmosbay.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > Do you have an idea of the performance gain we could expect from this node > local pda allocation ? I wouldn't expect very much. > Say a CPU is on Node 1, was a change in pda (allocated on Node 0) > immediatly mirrored on remote node or not ? The Opteron caches are write back afaik - this means data only leaves the L2 cache when other data pushes it out. But the additional traffic on the interconnect was likely negligible. If anything I would expect the reduced latency when a user space program eat up all cache and the PDA is needed on the next kernel entry to be helpful. But it's not very much at least on an Opteron because the NUMA factor isn't that bad. On Kiran's machines which likely have a higher NUMA factor I guess it helps more. -Andi