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 <[email protected]> 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 [email protected]. > 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 [email protected]. For more options, visit https://groups.google.com/d/optout.
