From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: 5x dom0 memory increase from Xen/Linux 3.4/2.6.18 to 4.1/3.0.0 Date: Thu, 16 Jun 2011 10:56:11 -0400 Message-ID: <20110616145611.GC6108@dumpdata.com> References: <10979454.29.1308229105101.JavaMail.root@zimbra.overnetdata.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <10979454.29.1308229105101.JavaMail.root@zimbra.overnetdata.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Anthony Wright Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On Thu, Jun 16, 2011 at 01:58:25PM +0100, Anthony Wright wrote: > I have a fairly old machine with 512M of RAM that I use for testing. Under Xen 3.4 with the 2.6.18 linux kernel it would happily work with dom0_mem=50M, leaving 450M for VMs. I am in the process of upgrading to Xen 4.1 with a stock 3.0.0-rc3 linux kernel (with konrad's vga-support patch). This combination however requires dom0_mem=250M to work leaving only 250M for the VMs (if I try to set dom0_mem any lower I get a kernel panic early on in the kernel boot phase). > > This is an increase of 5x between the two versions, and I wondered if there's an explanation why. Is it possible to reduce the memory requirements, or do I have to learn to live with it. The SWIOTLB is taking a 64MB chunk out of it. You could lower that by 'swiotlb=2048' or so. Also make sure to compile the CONFIG_XEN_MAX_DOMAIN_MEMORY from 128GB down to say 1. Besides that .. run with 'memblock=debug loglevel=10 initcall_debug debug' and see what other regions memblock reserves that could be shrunk. > > thanks, > > Anthony Wright > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel