* Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote: > On 09/22/09 01:09, Ingo Molnar wrote: > >>> kvm will be removing the pvmmu support soon; and Xen is talking about > >>> running paravirtualized guests in a vmx/svm container where they don't > >>> need most of the hooks. > >>> > >> We have no plans to drop support for non-vmx/svm capable processors, > >> let alone require ept/npt. > > > > But, just to map out our plans for the future, do you concur with > > the statements and numbers offered here by the VMware and KVM folks > > that on sufficiently recent hardware, hardware-assisted > > virtualization outperforms paravirt_ops in many (most?) workloads? > > Well, what Avi is referring to here is some discussions about a hybrid > paravirtualized mode, in which Xen runs a normal Xen PV guest within a > hardware container in order to get some immediate optimisations, and > allow further optimisations like using hardware assisted paging > extensions. > > For KVM and VMI, which always use a shadow pagetable scheme, hardware > paging is now unambigiously better than shadow pagetables, but for Xen > PV guests the picture is mixed since they don't use shadow pagetables. > The NPT/EPT extensions make updating the pagetable more efficent, but > actual access is more expensive because of the higher load on the TLB > and the increased expense of a TLB miss, so the actual performance > effects are very workload dependent. obviously they are workload dependent - that's why numbers were posted in this thread with various workloads. Do you concur with those conclusions that they are generally a speedup over paravirt? If not, which are the workloads where paravirt offers significant speedup over hardware acceleration? Ingo _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
