Virtualization

# What actually differs between a VM and a container: how many kernels boot.
VM_BOOT_MS, CONTAINER_START_MS = 2400, 40

class Hypervisor:
    """Type 1: each guest boots its own kernel on virtual hardware."""
    def __init__(self):
        self.kernels = 0
    def launch(self, n):
        self.kernels += n              # every guest brings a kernel
        return n * VM_BOOT_MS

class Kernel:
    """OS-level: one kernel, partitioned by namespaces and cgroups."""
    def __init__(self):
        self.kernels = 1               # the one already running
    def launch(self, n):
        return n * CONTAINER_START_MS  # nothing boots -- just restricted views

vm, host = Hypervisor(), Kernel()
vm.launch(3)
host.launch(3)

print(f"VM boot {VM_BOOT_MS}ms x3 = {vm.kernels} kernels "
      f"| container {CONTAINER_START_MS}ms x3 = {host.kernels} kernel shared")

#include <iostream>
using namespace std;
// What actually differs between a VM and a container: how many kernels boot.
const int VM_BOOT_MS = 2400, CONTAINER_START_MS = 40;
struct Hypervisor {   // Type 1: each guest boots its own kernel
    int kernels = 0;
    int launch(int n) {
        kernels += n;
        return n * VM_BOOT_MS;
    }
};
struct Kernel {   // OS-level: one kernel, partitioned
    int kernels = 1; // the one already running
    int launch(int n) {
        return n * CONTAINER_START_MS;
    }
    // nothing boots
};
int main() {
    Hypervisor vm;
    Kernel host;
    vm.launch(3);
    host.launch(3);
    cout << "VM boot " << VM_BOOT_MS << "ms x3 = " << vm.kernels
    << " kernels | container " << CONTAINER_START_MS << "ms x3 = "
    << host.kernels << " kernel shared\n";
}

class Main {
    // What differs between a VM and a container: how many kernels boot.
    static final int VM_BOOT_MS = 2400, CONTAINER_START_MS = 40;
    static class Hypervisor {   // Type 1: each guest boots its own kernel
        int kernels = 0;
        int launch(int n) {
            kernels += n;
            return n * VM_BOOT_MS;
        }
    }
    static class Kernel {   // OS-level: one kernel, partitioned
        int kernels = 1; // the one already running
        int launch(int n) {
            return n * CONTAINER_START_MS;
        }
        // nothing boots
    }
    public static void main(String[] args) {
        Hypervisor vm = new Hypervisor();
        Kernel host = new Kernel();
        vm.launch(3);
        host.launch(3);
        System.out.println("VM boot " + VM_BOOT_MS + "ms x3 = " + vm.kernels
        + " kernels | container " + CONTAINER_START_MS + "ms x3 = "
        + host.kernels + " kernel shared");
    }
}