On Thu, Nov 08, 2007 at 03:41:12PM -0600, Ryan Harper wrote: > * Daniel Veillard <veillard@xxxxxxxxxx> [2007-11-08 15:27]: > > yes, I understand and that's why I agreed to add the cpuset information > > at that point it's more than tunning because it may be irreversible for the > > lifetime of the domain, so this really should be in the XML. I'm not > > suggesting to go back about 'cpu affinity' i.e. to which physical CPUs > > a domain should be bound, but 'vcpu affinity' i.e. then how the virtual > > CPUs of the domain are mapped onto that cpu set, that can change > > OK, I see your distinction here. okay, good this is clarified, bear with me it's not always simple to try to explain this kind of things :-) > > dynamically without (serious) performance penalty. > > At least for Xen, the 'cpu' affinity specified with a domain is > only accessible via the xen config file and is not enforced in any way > such that it prevents from someone "tuning" a domain to use physical > cpus outside of the specified cpumap. Users can can certainly > specify a cpu outside of the original cpuset from the config file which > in a NUMA scenario has the potential for serious performance penalties. Well all tuning parameters I can think of can actually harm the system, actually if there was no drawback possible they would be integrated in the system default mechanism I guess :-) > > > > > I don't have any objection to separating "tuning" information as long as > > > we have the ability to merge permanent domain parameters with its > > > "tuning" information prior to domain construction. > > > > My point is that you don't need the tuning informations to create the > > domain, if you need them it's not tuning. When you say you want to > > merge them, do you want this to create the domain ? It should not > > be necessary (or I take a counter example that would help me), right ? > > I agree here. I was lumping cpuset info into your tunable category but > you clarified the distinction above. I just want to ensure that initial > cpuset mapping is present prior to constructing a domain as that is > integral for proper Xen NUMA memory allocation. okay, sure, that's clear in my mind but wasn't clear in my wording, I hope there is no other issue. 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/ -- Libvir-list mailing list Libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list