Versus

docker

Docker containers are fast, easy to use and largely free. In terms of performance, they have even been called comparable to KVM http://searchservervirtualization.techtarget.com/feature/Docker-containers-virtualization-can-work-in-harmony and http://bodenr.blogspot.ro/2014/05/kvm-and-docker-lxc-benchmarking-with.html
- docker is really fast
kvm top command return full list of processe, docker run only specific container, the rest are share with host machine!!!

Based on this testing environment, KVM is almost always within 2% of bare metal performance. Xen fell within 2.5% of bare metal performance in three out of ten tests but often had a variance of up to 5-7%. via https://major.io/2014/06/22/performance-benchmarks-kvm-vs-xen/

The VMWare I/O disk performance is mostly from 20 to 30% better than KVM, with a few exceptions. And generally the VMWare I/O performance is 10-15% less than the Bare Metal performance. via https://www.duo.uio.no/handle/10852/34900
Who isn’t using KVM? Likely (if not entirely) the people who already had something else in their data center. Larger organizations with investments in VMware, or other virtual infrastructures, want to retain those investments as they build their cloud more
- They got out of the box cloud solutions https://www.vmware.com/products/datacenter-virtualization/ . See https://www.leaseweb.com/cloud/private/VMware, https://www.rackspace.com/dedicated-servers/vmware. This is why fist glance google search could be a "false friend" !