On Fri, Jan 12, 2007 at 03:04:57PM +0100, Philippe Berthault wrote: > Daniel Veillard a écrit : > > I think Xen just returns -1 when the field is uninitialized, probably > >meaning 'all physical memory'. Once you use "xm mem-max 0 ..." then it > >consider the Dom0 domain constrained, but not before. And since there > >are machine where it's possible to hot plug new memory this is a way to > >not poll the current physical memory, a bit weird but that can be > >understood. > > > The signed value -1, "casted" in C/C++ in unsigned integer, gives the > value 4294967295. The Max memory value returned by virsh is 4294967292. > There is a small difference (3), so the value returned by Xen can't be -1. I think it's just a side effect of the conversion from pages number to kilobytes (assuming you're on a 4k page machine) 4294967292 is (((2^32 -1) /4 ) * 4) xen has -1, but the interface with xen usually count in page tables, and libvirt just multiplies later to get back to kB, leading to this rounding. Daniel -- Red Hat Virtualization group http://redhat.com/virtualization/ Daniel Veillard | virtualization library http://libvirt.org/ veillard@xxxxxxxxxx | libxml GNOME XML XSLT toolkit http://xmlsoft.org/ http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/