From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50483) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VkwK6-0003ek-8n for qemu-devel@nongnu.org; Mon, 25 Nov 2013 08:35:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VkwJx-0008Kr-OH for qemu-devel@nongnu.org; Mon, 25 Nov 2013 08:35:34 -0500 Received: from mail-qe0-x229.google.com ([2607:f8b0:400d:c02::229]:54431) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VkwJx-0008Kn-Jj for qemu-devel@nongnu.org; Mon, 25 Nov 2013 08:35:25 -0500 Received: by mail-qe0-f41.google.com with SMTP id gh4so1311001qeb.0 for ; Mon, 25 Nov 2013 05:35:25 -0800 (PST) Sender: Paolo Bonzini Message-ID: <52935216.90009@redhat.com> Date: Mon, 25 Nov 2013 14:35:18 +0100 From: Paolo Bonzini MIME-Version: 1.0 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> In-Reply-To: <1385379545.25009.22.camel@nilsson.home.kraxel.org> Content-Type: text/plain; charset=UTF-8 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: Gerd Hoffmann Cc: peter.maydell@linaro.org, stefanha@redhat.com, stefanb@linux.vnet.ibm.com, hutao@cn.fujitsu.com, mst@redhat.com, mjt@tls.msk.ru, qemu-devel@nongnu.org, mdroth@linux.vnet.ibm.com, vasilis.liaskovitis@profitbricks.com, quintela@redhat.com, aliguori@amazon.com, Igor Mammedov , marcel.a@redhat.com, lcapitulino@redhat.com, chegu_vinod@hp.com, afaerber@suse.de, armbru@redhat.com 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. Paolo