On 07/05/2013 05:15 AM, Laszlo Ersek wrote: > On 07/04/13 21:49, 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. > > See also the commit msg of its grandparent, eb7ee2cb, for general notes. > The containing series is d195325b^..1a0c0958. > > A more recent (and simpler) use is the 8ccbad5c^..0c764a9d sub-series.
Thank you for your references Laszlo, it's very helpful. Wanlong Gao > > Thanks for the reference, Paolo. > > Laszlo > >
