From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35846) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Vkx5m-0006tu-Hc for qemu-devel@nongnu.org; Mon, 25 Nov 2013 09:24:56 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Vkx5g-0006gT-Hg for qemu-devel@nongnu.org; Mon, 25 Nov 2013 09:24:50 -0500 Received: from mx1.redhat.com ([209.132.183.28]:31015) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Vkx5g-0006gO-81 for qemu-devel@nongnu.org; Mon, 25 Nov 2013 09:24:44 -0500 Date: Mon, 25 Nov 2013 15:24:27 +0100 From: Igor Mammedov Message-ID: <20131125152427.783ca25d@nial.usersys.redhat.com> In-Reply-To: <52935216.90009@redhat.com> References: <1385001528-12003-1-git-send-email-imammedo@redhat.com> <1385001528-12003-22-git-send-email-imammedo@redhat.com> <1385130236.3681.94.camel@nilsson.home.kraxel.org> <20131125120019.7b6d4140@nial.usersys.redhat.com> <1385379545.25009.22.camel@nilsson.home.kraxel.org> <52935216.90009@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 21/27] pc: add memory hotplug 440fx machine List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: peter.maydell@linaro.org, aliguori@amazon.com, mst@redhat.com, hutao@cn.fujitsu.com, stefanb@linux.vnet.ibm.com, mjt@tls.msk.ru, qemu-devel@nongnu.org, mdroth@linux.vnet.ibm.com, vasilis.liaskovitis@profitbricks.com, quintela@redhat.com, Gerd Hoffmann , stefanha@redhat.com, marcel.a@redhat.com, lcapitulino@redhat.com, chegu_vinod@hp.com, afaerber@suse.de, armbru@redhat.com On Mon, 25 Nov 2013 14:35:18 +0100 Paolo Bonzini wrote: > Il 25/11/2013 12:39, Gerd Hoffmann ha scritto: > >> > As use case 32-bit guest could start whit small initial memory > >> > and hotplug additional memory if needed up to point where 32-bit > >> > PCI hole starts. That would allow guests to launch with small amount > >> > but baloon up upto 2-3.5 Gb depending on machine type. > >> > I could drop 32-bit guest support and do only high mem hotplug if > >> > this case it not interesting to the comunity, any suggestions? > > 32bit limits start to hurt with 1GB already. Kernel address space is 1G > > on 32bit, so the kernel can't map all RAM all the time any more. Which > > in turn adds overhead for mapping/unmapping pages if the kernel must > > access highmem pages. So it's better to run 64bit guests even with alot > > less than 4G of memory. > > > > I'd tend to just not support 32bit guests, I think it simply isn't worth > > the trouble. > > Also because it's just non-PAE 32-bit guests, no? PAE guests would > support hotplug just fine. Yes, it shouldn't be issue for PAE in general. but it might not work for Windows Server 2003 (including 64-bit one), since it BSODed when it sees 64bit CRS (we saw it playing with 64-bit PCI window). Not sure if we care about it though. > Paolo >