From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d01relay02.pok.ibm.com (d01relay02.pok.ibm.com [9.56.227.234]) by e6.ny.us.ibm.com (8.12.11/8.12.11) with ESMTP id j9LG13tP027922 for ; Fri, 21 Oct 2005 12:01:03 -0400 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay02.pok.ibm.com (8.12.10/NCO/VERS6.7) with ESMTP id j9LG13gZ046776 for ; Fri, 21 Oct 2005 12:01:03 -0400 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.12.11/8.13.3) with ESMTP id j9LG12Yv009939 for ; Fri, 21 Oct 2005 12:01:03 -0400 Date: Fri, 21 Oct 2005 09:00:56 -0700 From: mike kravetz Subject: Re: [PATCH 0/4] Swap migration V3: Overview Message-ID: <20051021160056.GA32741@w-mikek2.ibm.com> References: <20051020225935.19761.57434.sendpatchset@schroedinger.engr.sgi.com> <20051020160638.58b4d08d.akpm@osdl.org> <20051020234621.GL5490@w-mikek2.ibm.com> <20051021082849.45dafd27.pj@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051021082849.45dafd27.pj@sgi.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Paul Jackson Cc: akpm@osdl.org, clameter@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, magnus.damm@gmail.com, marcelo.tosatti@cyclades.com List-ID: On Fri, Oct 21, 2005 at 08:28:49AM -0700, Paul Jackson wrote: > Mike wrote: > > Just to be clear, there are at least two distinct requirements for hotplug. > > One only wants to remove a quantity of memory (location unimportant). > > Could you describe this case a little more? I wasn't aware > of this hotplug requirement, until I saw you comment just now. Think of a system running multiple OS's on top of a hypervisor, where each OS is given some memory for exclusive use. For multiple reasons (one being workload management) it is desirable to move resources from one OS to another. For example, take memory away from an underutilized OS and give it to an over utilized OS. This describes the environment on IBM's mid to upper level POWER systems. Currently, there is OS support to dynamically move/reassign CPUs and adapters between different OSs on these systems. My knowledge of Xen is limited, but this might also apply to that environment also. An interesting question comes up if Xen or some other hypervisor starts vitrtualizing memory. In such cases, would it make more sense to allow the hypervisor do all resizing or do we also need hotplug support in the OS for optimal performance? -- Mike -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org