CPU and Memory Performance Tuning

Overview

Optimize Proxmox VE for maximum performance through CPU pinning, memory management, and NUMA configuration.

CPU Pinning

What is CPU Pinning

CPU pinning binds VM vCPUs to specific physical CPU cores, reducing context switching overhead.

Pin VM to Cores

# Pin to cores 0-3
qm set 100 --cores 4 --cpuset 0-3
 
# Pin to cores 0,2,4,6 (even cores)
qm set 100 --cpuset 0,2,4,6
 
# Pin specific cores
qm set 100 --cpulimit 2 --cpuunits 1024

Options Explained

Option	Description
—cores	Number of vCPUs
—cpuset	Physical cores to use
—cpulimit	CPU limit (%)
—cpuunits	CPU weight (0-1024)

Multi-Socket NUMA

# Enable NUMA
qm set 100 --numa 1
 
# Configure NUMA node
qm set 100 --numa0 memory=4096,cpus=0-3
 
# Second NUMA node
qm set 100 --numa1 memory=4096,cpus=4-7

Huge Pages

Enable Huge Pages

# Enable 2MB huge pages
qm set 100 --hugepages 1024
 
# Enable 1GB huge pages
qm set 100 --hugepages 1
 
# Check current huge pages
cat /proc/meminfo | grep -i huge

Configure Host Huge Pages

# Allocate huge pages
echo 1024 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
 
# Check allocation
cat /proc/meminfo | grep -i huge
 
# Make persistent
echo "hugepages=1024" >> /etc/default/grub
update-grub

Huge Page Sizes

Size	Use Case
2MB	General workloads
1GB	Large databases, HPC

Memory Optimization

Memory Ballooning

# Disable balloon (for performance VMs)
qm set 100 --balloon 0
 
# Set minimum balloon
qm set 100 --balloon 4096
 
# Configure balloon drivers in guest
# Linux: apt install pciutils
# Windows: Install balloon driver

Memory Locking

# Lock memory (prevent swap)
qm set 100 --lockmemory 1
 
# Check memory in guest
cat /sys/kernel/mm/transparent_hugepage/enabled

NUMA Memory

# Enable NUMA
qm set 100 --numa 1
 
# Auto NUMA
qm set 100 --numa auto=1

I/O Optimization

I/O Thread

# Enable I/O thread
qm set 100 --iothread 1
 
# Add to VirtIO disk
qm set 100 --scsi0 local:,iothread=1,discard=1,ssd=1

VirtIO Drivers

# Optimal VirtIO config
qm set 100 --scsi0 local:,cache=none,iothread=1
 
# Enable discard
qm set 100 --scsi0 local:,discard=1
 
# SSD emulation
qm set 100 --scsi0 local:,ssd=1

Disk Options

Option	Description
cache=none	No host cache
cache=writeback	Write back
discard=1	TRIM support
ssd=1	SSD emulation
iothread=1	I/O thread

Network Optimization

VirtIO Multi-Queue

# Enable multi-queue (4 queues)
qm set 100 --net0 virtio,bridge=vmbr0,queues=4
 
# Update running VM
qm set 100 --net0 virtio,bridge=vmbr0, queues=8
 
# Maximum 16 queues

Network Options

Option	Description
queues=N	Number of queues
rx=N	RX queues
tx=N	TX queues

Packet Steering

# RSS configuration in guest
ethtool -L eth0 combined 4

CPU Mode Optimization

Host CPU Mode

# Use host CPU (best performance)
qm set 100 --cpu host
 
# Enable flags
qm set 100 --cpu host --flags +vmx,+svm
 
# Specific CPU type
qm set 100 --cpu Penryn
qm set 100 --cpu Haswell-noTSX

CPU Flags

Flag	Description
+vmx	Intel VT-x
+svm	AMD-V
+aes	AES-NI
+avx	AVX
+avx2	AVX2

Real-Time Performance

Enable Real-Time

# Configure real-time
qm set 100 --realtime 1
 
# Set CPU mask
qm set 100 --cpumask 0-3

RT Kernel

# Install RT kernel
apt install proxmox-kernel-real-time
 
# Update GRUB
update-grub
reboot

Benchmarking

CPU Benchmark

# In VM: sysbench
sysbench cpu --cpu-max-prime=20000 run
 
# In VM: stress
stress --cpu 4

Memory Benchmark

# In VM: sysbench
sysbench memory --memory-block-size=1M --memory-total-size=10G run

Disk Benchmark

# In VM: fio
fio --name=seqread --ioengine=libaio --direct=1 --bs=4k --numjobs=1 --rw=read --size=1G --runtime=30 --filename=/tmp/test
 
# Or: dd
dd if=/dev/zero of=/tmp/test bs=4k count=250000 oflag=direct

Monitoring

Performance Metrics

# CPU usage
pvesh get /nodes/localhost/status
 
# VM stats
qm monitor 100
 
# Memory
qm exec 100 -- cat /proc/meminfo
 
# In guest commands
pct exec 100 -- cat /proc/meminfo

Real-Time Monitoring

# Monitor VM
qm start 100
 
# Watch stats
watch -n1 "qm exec 100 -- cat /proc/stat"

Quick Reference

Optimization Checklist

# CPU
qm set 100 --cpu host --cores 4
 
# Memory
qm set 100 --balloon 0 --lockmemory 1
 
# NUMA
qm set 100 --numa 1
 
# I/O Thread
qm set 100 --iothread 1
 
# Network
qm set 100 --net0 virtio,bridge=vmbr0,queues=4

Keywords

performance cpu-pinning huge-pages numa optimization io-thread real-time

Related Articles

• Advanced
• Nested-Virtualization
• SR-IOV
• Storage-Advanced

---

Back to Proxmox VE