On 07/05/2013 03:49 AM, Paolo Bonzini wrote: > Il 04/07/2013 11:53, Wanlong Gao ha scritto: >> As you know, QEMU can't direct it's memory allocation now, this may cause >> guest cross node access performance regression. >> And, the worse thing is that if PCI-passthrough is used, >> direct-attached-device uses DMA transfer between device and qemu process. >> All pages of the guest will be pinned by get_user_pages(). >> >> KVM_ASSIGN_PCI_DEVICE ioctl >> kvm_vm_ioctl_assign_device() >> =>kvm_assign_device() >> => kvm_iommu_map_memslots() >> => kvm_iommu_map_pages() >> => kvm_pin_pages() >> >> So, with direct-attached-device, all guest page's page count will be +1 and >> any page migration will not work. AutoNUMA won't too. >> >> So, we should set the guest nodes memory allocation policy before >> the pages are really mapped. >> >> According to this patch set, we are able to set guest nodes memory policy >> like following: >> >> -numa node,nodeid=0,mem=1024,cpus=0,mem-policy=membind,mem-hostnode=0-1 >> -numa node,nodeid=1,mem=1024,cpus=1,mem-policy=interleave,mem-hostnode=1 > > Did you see my suggestion to use instead something like this: > > -numa node,nodeid=0,cpus=0 -numa node,nodeid=1,cpus=1 \ > -numa mem,nodeid=0,size=1G,policy=membind,hostnode=0-1 > -numa mem,nodeid=1,size=2G,policy=interleave,hostnode=1 > > With an eye to when we'll support memory hotplug, I think it is better. > It is not hard to implement it using the OptsVisitor; see > 14aa0c2de045a6c2fcfadf38c04434fd15909455 for an example of a complex > schema described with OptsVistor.
OK, got it, thank you. Wanlong Gao > > Paolo > >
