Zachary Amsden wrote: > In general, I/O in a virtual guest is subject to performance > problems. The I/O can not be completed physically, but must be > virtualized. This means trapping and decoding port I/O instructions > from the guest OS. Not only is the trap for a #GP heavyweight, both > in the processor and the hypervisor (which usually has a complex #GP > path), but this forces the hypervisor to decode the individual > instruction which has faulted. Worse, even with hardware assist such > as VT, the exit reason alone is not sufficient to determine the true > nature of the faulting instruction, requiring a complex and costly > instruction decode and simulation. > > This patch provides hypercalls for the i386 port I/O instructions, > which vastly helps guests which use native-style drivers. For certain > VMI workloads, this provides a performance boost of up to 30%. We > expect KVM and lguest to be able to achieve similar gains on I/O > intensive workloads. > Won't these workloads be better off using paravirtualized drivers? i.e., do the native drivers with paravirt I/O instructions get anywhere near the performance of paravirt drivers? -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
