So forgive my lack of kvm/qemu knowledge but I couldn’t find anything on Google on this. If you deployed an instance of a different architecture than the physical CPU, wouldn’t qemu just emulate the processor (if you were in virt_type=kvm) mode, or would libvirt throw some error?
Thanks, Jared Jared Wilkinson | Infrastructure Engineer – Systems jwilkin...@ebsco.com | (W) 205/981-4018 | (M) 205/259-9802 5724 US Highway 280 East, Birmingham, AL 35242, USA On 5/3/16, 10:01 AM, "Daniel P. Berrange" <berra...@redhat.com> wrote: >Hello Operators, > >One of the things that constantly puzzles me when reading the user >survey results wrt hypervisor is the high number of respondants >claiming to be using QEMU (as distinct from KVM). > >As a reminder, in Nova saying virt_type=qemu causes Nova to use >plain QEMU with pure CPU emulation which is many many times slower >to than native CPU performance, while virt_type=kvm causes Nova to >use QEMU with KVM hardware CPU acceleration which is close to native >performance. > >IOW, virt_type=qemu is not something you'd ever really want to use >unless you had no other options due to the terrible performance it >would show. The only reasons to use QEMU are if you need non-native >architecture support (ie running arm/ppc on x86_64 host), or if you >can't do KVM due to hardware restrictions (ie ancient hardware, or >running compute hosts inside virtual machines) > >Despite this, in the 2016 survey 10% claimed to be using QEMU in >production & 3% in PoC and dev, in 2014 it was even higher at 15% >in prod & 12% in PoC and 28% in dev. > >Personally my gut feeling says that QEMU usage ought to be in very >low single figures, so I'm curious as to the apparent anomoly. > >I can think of a few reasons > > 1. Respondants are confused as to the difference between QEMU > and KVM, so are saying QEMU, despite fact they are using KVM. > > 2. Respondants are confused as to the difference between QEMU > and KVM, so have mistakenly configured their nova hosts to > use QEMU instead of KVM and suffering poor performance without > realizing their mistake. > > 3. There are more people than I expect who are running their > cloud compute hosts inside virtual machines, and thus are > unable to use KVM. > > 4. There are more people than I expect who are providing cloud > hosting for non-native architectures. eg ability to run an > arm7/ppc guest image on an x86_64 host and so genuinely must > use QEMU > >If items 1 / 2 are the cause, then by implication the user survey >is likely under-reporting the (already huge) scale of the KVM usage. > >I can see 3. being a likely explanation for high usage of QEMU in a >dev or PoC scenario, but it feels unlikely for a production deployment. > >While 4 is technically possible, Nova doesn't really do a very good >job at mixed guest arch hosting - I'm pretty sure there are broken >pieces waiting to bite people who try it. > >Does anyone have any thoughts on this topic ? > >Indeed, is there anyone here who genuinely use virt_type=qemu in a >production deployment of OpenStack who might have other reasons that >I've missed ? > >Regards, >Daniel >-- >|: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| >|: http://libvirt.org -o- http://virt-manager.org :| >|: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| >|: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| > >_______________________________________________ >OpenStack-operators mailing list >OpenStack-operators@lists.openstack.org >http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators _______________________________________________ OpenStack-operators mailing list OpenStack-operators@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators
