FWIW: KVM is a type-2 hypervisor, Xen (and ACRN and a few others) are type-1. Both have advantages and disadvantages.
For example, a type-2 hypervisor is very difficult to tune for running RT OSes while ACRN (and even Xen lately -- especially on ARM) do it with no sweat. Thanks, Roman. On Mon, Feb 18, 2019 at 11:21 PM Joe Duarte <songofapo...@gmail.com> wrote: > > > On Monday, February 18, 2019 at 1:43:29 PM UTC-8, Nadav Har'El wrote: >> >> >> >> KVM and Xen are *hypervisors*, i.e., software which allows running >> multiple virtual-machines on one physical machine. >> The "Linux scheduler" and "Xen scheduler" you mention are implementation >> details of that hypervisor, and has nothing to do with OSv. >> >> > Right, I know all that. What I was saying is that KVM is supposed to have > an *advantage* over Xen because there's only one scheduler, because while > KVM is technically a hypervisor, it's in the Linux kernel (not underneath > it like Xen). I got this point from Brendan Gregg, a performance engineer > at Joyent and now Netflix. One place he touches on it is in this doc > <http://www.brendangregg.com/Articles/Virtualization_Performance_Zones_KVM_Xen.pdf>: > "With KVM, the hypervisor is a kernel module (kvm) which is scheduled by > the OS scheduler. It can be tuned using the usual OS kernel scheduler > classes, policies and priorities. The I/O path takes fewer steps than Xen." > > I took this as having implications for OSv since OSv also runs on top of > Xen with, apparently, its own scheduler. (I don't know if it's restricted > to Xen anymore.) I don't know if or how the schedulers interact. Is OSv I/O > (on Xen) faster than KVM VM I/O? Table 1 from the paper might bear on it, > but it's five years old and I'm not clear as to what the Linux setup was > (was it Fedora 20 running KVM with a Fedora 20 guest on top?). > > JD > > -- > You received this message because you are subscribed to the Google Groups > "OSv Development" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to osv-dev+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "OSv Development" group. To unsubscribe from this group and stop receiving emails from it, send an email to osv-dev+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
