On 06/28/2012 09:07 AM, Tomoki Sekiyama wrote: > Hello, > > This RFC patch series provides facility to dedicate CPUs to KVM guests > and enable the guests to handle interrupts from passed-through PCI devices > directly (without VM exit and relay by the host). > > With this feature, we can improve throughput and response time of the device > and the host's CPU usage by reducing the overhead of interrupt handling. > This is good for the application using very high throughput/frequent > interrupt device (e.g. 10GbE NIC). > CPU-intensive high performance applications and real-time applicatoins > also gets benefit from CPU isolation feature, which reduces VM exit and > scheduling delay. > > Current implementation is still just PoC and have many limitations, but > submitted for RFC. Any comments are appreciated. > > * Overview > Intel and AMD CPUs have a feature to handle interrupts by guests without > VM Exit. However, because it cannot switch VM Exit based on IRQ vectors, > interrupts to both the host and the guest will be routed to guests. > > To avoid mixture of host and guest interrupts, in this patch, some of CPUs > are cut off from the host and dedicated to the guests. In addition, IRQ > affinity of the passed-through devices are set to the guest CPUs only. > > For IPI from the host to the guest, we use NMIs, that is an only interrupts > having another VM Exit flag. > > * Benefits > This feature provides benefits of virtualization to areas where high > performance and low latency are required, such as HPC and trading, > and so on. It also useful for consolidation in large scale systems with > many CPU cores and PCI devices passed-through or with SR-IOV. > For the future, it may be used to keep the guests running even if the host > is crashed (but that would need additional features like memory isolation). > > * Limitations > Current implementation is experimental, unstable, and has a lot of limitations. > - SMP guests don't work correctly > - Only Linux guest is supported > - Only Intel VT-x is supported > - Only MSI and MSI-X pass-through; no ISA interrupts support > - Non passed-through PCI devices (including virtio) are slower > - Kernel space PIT emulation does not work > - Needs a lot of cleanups > This is both impressive and scary. What is the target scenario here? Partitioning? I don't see this working for generic consolidation. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
