When configuring KVM virtualization on your 8-core/16GB host, the key principle is that virtual resources can be overcommitted, but with important caveats:

# Check available CPU threads
grep -c ^processor /proc/cpuinfo

# Check available memory
free -h

For CPU-intensive workloads, follow these guidelines:

• Total assigned vCPUs can exceed physical cores (CPU overcommit)
• Performance penalty begins at ~1.5:1 overcommit ratio
• For 8 cores: Safe maximum is 12 vCPUs (4 VMs × 3 vCPUs)

Memory cannot be overcommitted like CPU resources. Your 16GB host should reserve:

# Recommended minimum host reservation:
- 1GB for host OS
- 512MB per VM for QEMU overhead

Sample allocation for 4 VMs:

Total RAM: 16GB
Host reservation: 1GB
QEMU overhead: 4×512MB = 2GB
Available for VMs: 13GB
Per VM allocation: 3.25GB

Here's a libvirt domain XML snippet for optimal 4-VM setup:

<domain type='kvm'>
  <name>vm1</name>
  <memory unit='GiB'>3.25</memory>
  <vcpu placement='static'>2</vcpu>
  <cpu mode='host-passthrough'/>
  <os>
    <type arch='x86_64'>hvm</type>
  </os>
</domain>

Essential commands to verify resource utilization:

# CPU load
virsh vcpuinfo vm1
mpstat -P ALL 1

# Memory usage
virsh dommemstat vm1
watch -n 1 "egrep '^(MemFree|Buffers|Cached)' /proc/meminfo"

For production environments, consider these /etc/libvirt/qemu.conf settings:

vcpupin = [
    [ "0", "1", "2", "3" ],
    [ "4", "5", "6", "7" ]
]
emulatorpin = "0-7"
memory_backing = "hugepages=on"

When configuring KVM virtualization on your 8-core/16GB host, the key principle is that virtual resources can be overcommitted, but physical resources cannot. For CPU cores, KVM supports CPU overcommitment through time-sharing, while memory overcommitment requires special techniques like KSM (Kernel Samepage Merging).

For your specific hardware (8 cores/16GB RAM), here are valid allocation examples:

# Example 1: Balanced allocation for 4 VMs
virsh edit vm1
<vcpu placement='static'>2</vcpu>
<memory unit='KiB'>4194304</memory>

# Example 2: Overcommitted CPU scenario
virsh edit vm2
<vcpu placement='static'>4</vcpu>  # 4 VMs × 4 vCPUs = 16 vCPUs (2× overcommit)

The host OS typically needs:

• Minimum 1 physical core (though 2 is recommended for stability)
• 1-2GB RAM for base operations plus 100-200MB per running VM
• Additional resources for storage/network I/O processing

To maximize your hardware utilization:

# Enable KSM for memory deduplication:
echo 1 > /sys/kernel/mm/ksm/run

# Set CPU pinning for performance-critical VMs:
virsh vcpupin vm1 0 0  # Pin vCPU 0 to physical core 0
virsh vcpupin vm1 1 1  # Pin vCPU 1 to physical core 1

Essential commands for resource monitoring:

# Check CPU utilization
virsh vcpuinfo vm1

# Monitor memory usage
virsh dommemstat vm1

# View NUMA topology (important for multi-socket hosts)
virsh capabilities | grep -A10 "topology"