Performance Troubleshooting

Diagnose and fix performance problems on Pimeleon router

Performance Troubleshooting

"The speed of your system is inversely proportional to the urgency of your need." - Murphy's Law of Computing

Is your Pimeleon router running slower than expected? This guide helps identify and resolve performance issues.

Expected Performance

Typical Benchmarks

Raspberry Pi 4 / Pi 5:

  • Throughput: Excellent performance for gigabit connections (wired)
  • WiFi Speed: 50-100 Mbps (2.4 GHz)
  • Latency: < 2ms (local), 10-30ms (internet)
  • Max Clients: Typical home network device count

Raspberry Pi 3B+:

  • Throughput: Suitable for broadband connections (wired, USB 2.0 bus limitation creates a performance ceiling)
  • WiFi Speed: 40-80 Mbps (2.4 GHz)
  • Latency: < 5ms (local), 10-30ms (internet)
  • Max Clients: Typical home network device count

Quick Performance Check

Run these commands to assess current performance:

ssh pi@your-router-ip

# Check system load
uptime
# Load should be < 1.0 per CPU core

# Check temperature
vcgencmd measure_temp
# Should be < 70°C

# Check memory
free -h
# Should have > 100MB free

# Check CPU throttling
vcgencmd get_throttled
# 0x0 = no throttling

Slow Internet Speed

Test Your Speed

From client device:

# Install speedtest-cli
pip install speedtest-cli

# Run speed test
speedtest-cli

From router:

ssh pi@your-router-ip
curl -s https://raw.githubusercontent.com/sivel/speedtest-cli/master/speedtest.py | python3 -

Common Causes

1. ISP Speed Limitation

  • Test speed directly from modem (bypass router)
  • If similar speeds, ISP is the bottleneck

2. WiFi Interference

# Scan for nearby networks
iwlist wlan0 scan | grep -E "Channel|Signal"

# Switch to less crowded channel (1, 6, or 11)
sudo nano /etc/hostapd/hostapd.conf
# Change channel= line
sudo systemctl restart hostapd

3. Too Many Connected Devices

# Count active connections
arp -n | grep -v incomplete | wc -l

# View bandwidth usage by device
sudo iftop -i eth1

4. CPU Bottleneck

# Check CPU usage
top

# If consistently > 80%, identify culprit
ps aux --sort=-%cpu | head -10

High Latency (Lag)

Measure Latency

# To router (should be < 5ms)
ping -c 100 192.168.76.1

# To internet gateway (should be < 20ms)
ping -c 100 your-isp-gateway

# To internet (varies by distance)
ping -c 100 8.8.8.8

Diagnose High Latency

If high latency to router itself:

  1. Check WiFi signal strength
    # On device if Linux
iwconfig wlan0
# Look for Signal level
  2. Check for buffer bloat
    # Test with bufferbloat test
# Visit: https://www.waveform.com/tools/bufferbloat
  3. Check CPU load
    uptime
# If load > CPU cores, system is overloaded

If high latency only to internet:

  1. Trace route to identify problem
    mtr --report 8.8.8.8
# Look for hop with high latency
  2. Check your ISP's gateway
    ping your-isp-gateway
# If high here, contact ISP

WiFi Performance Issues

Slow WiFi Speed

Test WiFi speed:

# From device connected to WiFi
speedtest-cli

Compare to wired speed:

  • Connect same device via Ethernet
  • Run speed test again
  • WiFi should be 50-70% of wired speed

Optimization steps:

  1. Change WiFi channel
    sudo nano /etc/hostapd/hostapd.conf
# Set channel to 1, 6, or 11
channel=6
sudo systemctl restart hostapd
  2. Improve signal strength
    • Move router to central location
    • Remove obstructions (walls, metal objects)
    • Keep away from microwave, cordless phones
  3. Enable 802.11n optimizations (advanced)
    sudo nano /etc/hostapd/hostapd.conf
# Add these lines
ht_capab=[HT40+][SHORT-GI-20][SHORT-GI-40]
sudo systemctl restart hostapd

    Note: Test thoroughly - may cause compatibility issues with older devices.

WiFi Keeps Dropping

Check connection stability:

# On WiFi device, continuous ping
ping -i 1 192.168.76.1
# Watch for dropped packets

Common fixes:

  1. iOS device disconnecting (very common)
    sudo nano /etc/hostapd/hostapd.conf
# Add/verify these lines exist:
beacon_int=100
dtim_period=2
ap_max_inactivity=300
skip_inactivity_poll=1
disassoc_low_ack=0

sudo systemctl restart hostapd
  2. Power management issues
    # Check WiFi power management
iwconfig wlan0 | grep "Power Management"

# Disable if enabled
sudo iwconfig wlan0 power off
  3. Too many clients
    # Count WiFi clients
iw dev wlan0 station dump | grep Station | wc -l

# If > 30, consider upgrading Pi model

Overheating Issues

Check Temperature

# Current temperature
vcgencmd measure_temp

# Monitor continuously
watch -n 1 vcgencmd measure_temp

Temperature Guidelines:

  • < 60°C: Excellent
  • 60-70°C: Good
  • 70-80°C: Warm (add cooling)
  • > 80°C: Hot (throttling likely)
  • > 85°C: Critical (add cooling immediately)

Check for Throttling

vcgencmd get_throttled

Output meanings:

  • 0x0: No issues
  • 0x1: Under-voltage detected
  • 0x2: ARM frequency capped
  • 0x4: Currently throttled
  • 0x8: Soft temperature limit

Cooling Solutions

  1. Passive cooling:
    • Add heatsinks to CPU and chips
    • Use metal case with thermal contact
  2. Active cooling:
    • Install 30mm or 40mm fan
    • Use official Pi 4 case with fan
  3. Improve airflow:
    • Don't enclose in tight space
    • Keep vents clear
    • Position with components facing up

Memory Issues

Check Memory Usage

# Current memory status
free -h

# Processes using most memory
ps aux --sort=-%mem | head -10

Warning signs:

  • Swap usage > 100MB
  • Available memory < 100MB
  • OOM (Out of Memory) errors in logs

Free Up Memory

# Clear caches
sync
echo 3 | sudo tee /proc/sys/vm/drop_caches

# Stop unnecessary services
sudo systemctl stop service-name

# Check for memory leaks
# Monitor process memory over time
watch -n 5 'ps aux | grep process-name'

Disk Performance

Check SD Card Speed

# Write speed test
dd if=/dev/zero of=/tmp/test bs=8k count=10k
# Should be > 10 MB/s

# Read speed test
dd if=/tmp/test of=/dev/null bs=8k
# Should be > 20 MB/s

# Clean up
rm /tmp/test

If slow:

  • SD card may be fake or low-quality
  • SD card may be failing
  • Try different SD card (SanDisk, Samsung recommended)

Check Disk Space

# Overall disk usage
df -h

# Find large directories
du -sh /* 2>/dev/null | sort -h

# Clean up if needed
sudo apt clean
sudo apt autoremove
sudo journalctl --vacuum-time=7d

Network Bandwidth Saturation

Monitor Real-Time Traffic

# Install monitoring tools
sudo apt install iftop nethogs

# Monitor interface bandwidth
sudo iftop -i eth1

# Monitor by process
sudo nethogs

Identify Bandwidth Hogs

# Active connections
ss -tuanp | grep ESTAB

# Connections by IP
ss -tan | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -nr

# Check for excessive connections
conntrack -C

Limit Bandwidth (QoS)

# Basic traffic shaping
sudo apt install wondershaper

# Limit interface to 50 Mbps down, 10 Mbps up
sudo wondershaper eth1 51200 10240

# Remove limits
sudo wondershaper clear eth1

DNS Performance

Test DNS Speed

# Measure DNS query time
time nslookup google.com

# Should be < 100ms

Optimize DNS

DNS Filtering:

# Update gravity database
pihole -g

# Clear cache
pihole restartdns

# Check blocked queries aren't slowing down
pihole -c

If using BIND:

# Flush cache
sudo rndc flush

# Check forwarders are responsive
dig @8.8.8.8 google.com

# Consider changing forwarders
sudo nano /etc/bind/named.conf.options

Multiple Devices Slow

Check Connection Limit

# Current connections
conntrack -C

# Maximum connections
cat /proc/sys/net/netfilter/nf_conntrack_max

# Increase if needed (requires reboot)
echo "net.netfilter.nf_conntrack_max=65536" | sudo tee -a /etc/sysctl.conf

Verify DHCP Isn't Exhausted

# Check active leases
sudo cat /var/lib/dhcp/dhcpd.leases | grep lease | wc -l

# Check configured range
sudo grep range /etc/dhcp/dhcpd.conf

# Expand range if needed

Optimization Tips

System Optimizations

# Disable unnecessary services
sudo systemctl disable bluetooth
sudo systemctl disable hciuart

# Optimize network stack
sudo sysctl -w net.core.rmem_max=134217728
sudo sysctl -w net.core.wmem_max=134217728

# Make permanent
echo "net.core.rmem_max=134217728" | sudo tee -a /etc/sysctl.conf
echo "net.core.wmem_max=134217728" | sudo tee -a /etc/sysctl.conf

WiFi Optimizations

sudo nano /etc/hostapd/hostapd.conf

# Optimize for performance
wmm_enabled=1
ieee80211n=1
require_ht=1

# Restart to apply
sudo systemctl restart hostapd

Hardware Upgrades

When to Upgrade

Consider upgrading if:

  • Consistently maxing out CPU (load > cores)
  • Regular thermal throttling
  • Need high throughput for gigabit connections
  • Supporting large network device counts
  1. From Pi 3B+ to Pi 4:
    • 3x faster CPU
    • Gigabit Ethernet (not USB-limited)
    • Better thermal performance
  2. From Pi 4 to Pi 5:
    • 2x faster CPU
    • Better I/O performance
    • Improved thermal management
  3. SD Card to SSD:
    • 10-20x faster disk I/O
    • More reliable
    • Better for heavy logging

Monitoring Performance

Setup Continuous Monitoring

# Create monitoring script
cat > ~/monitor.sh << 'EOF'
#!/bin/bash
while true; do
    clear
    echo "=== System Monitor ==="
    echo "Time: $(date)"
    echo ""
    echo "Load: $(uptime | awk -F'load average:' '{print $2}')"
    echo "Temp: $(vcgencmd measure_temp)"
    echo "Memory: $(free -h | grep Mem | awk '{print $3 "/" $2}')"
    echo "Throttled: $(vcgencmd get_throttled)"
    echo ""
    echo "Top Processes (CPU):"
    ps aux --sort=-%cpu | head -5 | awk '{print $11" "$3"%"}'
    echo ""
    echo "Network:"
    ifconfig eth1 | grep "RX packets"
    ifconfig eth1 | grep "TX packets"
    sleep 5
done
EOF

chmod +x ~/monitor.sh
~/monitor.sh

Getting Help

Collect Performance Data

# Generate performance report
cat > ~/perf-report.txt << EOF
Date: $(date)
Uptime: $(uptime)
Temperature: $(vcgencmd measure_temp)
Throttling: $(vcgencmd get_throttled)
Memory: $(free -h)
Disk: $(df -h /)
Load Average: $(uptime | awk -F'load average:' '{print $2}')

Top CPU Processes:
$(ps aux --sort=-%cpu | head -10)

Top Memory Processes:
$(ps aux --sort=-%mem | head -10)

Network Interfaces:
$(ip -s link show)

Active Connections:
$(ss -s)
EOF

cat ~/perf-report.txt

Support

For questions or issues:

ON THIS PAGE
Expected Performance
Quick Performance Check
Slow Internet Speed
High Latency (Lag)
WiFi Performance Issues
Overheating Issues
Memory Issues
Disk Performance
Network Bandwidth Saturation
DNS Performance
Multiple Devices Slow
Optimization Tips
Hardware Upgrades
Monitoring Performance
Getting Help
Related Documentation
Support