From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932119AbWIFHiZ (ORCPT ); Wed, 6 Sep 2006 03:38:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751630AbWIFHiY (ORCPT ); Wed, 6 Sep 2006 03:38:24 -0400 Received: from mail.suse.de ([195.135.220.2]:21898 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S1751628AbWIFHiY (ORCPT ); Wed, 6 Sep 2006 03:38:24 -0400 From: Andi Kleen To: Nick Piggin Subject: Re: [Feature] x86_64 page tracking for Stratus servers Date: Wed, 6 Sep 2006 09:36:19 +0200 User-Agent: KMail/1.9.3 Cc: Kimball Murray , linux-kernel@vger.kernel.org, akpm@digeo.com References: <20060905173229.14149.60535.sendpatchset@dhcp83-86.boston.redhat.com> <44FE6CD6.4040809@yahoo.com.au> In-Reply-To: <44FE6CD6.4040809@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200609060936.19268.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > Silly question, why can't you do all this from stop_machine_run context (or > your SMI) that doesn't have to worry about other CPUs dirtying memory? Because that would be too slow for continuous mirroring. You can't go through 10+GB of virtual memory (or more with shared memory because the scan has to be virtual) in an interrupt. The only sane way is to do it continuously. > [*] Though if it gets included, it would not stop me lamenting the > proliferation of complexities to support *tiny* obscure userbases. Can > we wait until your hardware is smart enough to snoop the cc? :) My guess is that if we had a generic memory mirror subsystem other people would find uses for it too. e.g. a lot of systems support spare DIMMs these days and mirroring some memory to it seems like a smart idea. That means normally the hardware does it, but perhaps some stuff can be done better by doing it in software. Or it is also a bit similar to the algorithms Xen uses for live migration. If that was implemented on the kernel level something like this might be useful too. I think OpenVZ has some kind of migration support, but it's currently not live. -andi