Swap
Category:Installation
Swap Configuration
Swap usage leads to performance degradation on VoIPmonitor servers. For realtime packet processing, we highly recommend configuring swap space properly or disabling it entirely.
Understanding Swappiness
Most Linux distributions default to using swap when RAM usage exceeds 40%. The swappiness value controls this behavior:
# Check current swappiness value
cat /proc/sys/vm/swappiness
A value of 60 means the system starts using swap when less than 60% of RAM is free. This is not optimal for realtime services like VoIPmonitor.
| Swappiness Value | Behavior |
|---|---|
| 0 | Use swap only when RAM is completely exhausted |
| 5 | Use swap only when critically low on RAM (recommended) |
| 60 | Default - start swapping at 40% free RAM (not recommended) |
| 100 | Aggressively use swap (not recommended for VoIPmonitor) |
Configuring Swappiness
Temporary Change (Until Reboot)
# Set swappiness to 5 (use swap only when critically low on RAM)
echo '5' > /proc/sys/vm/swappiness
# Apply immediately by clearing swap
swapoff -a && swapon -a
Permanent Change
Add the following line to /etc/sysctl.conf:
vm.swappiness=5
Then apply without reboot:
sysctl -p
Clearing Swap
To move all data from swap back to RAM:
swapoff -a
swapon -a
Disabling Swap Completely
- Step 1
- Disable swap immediately:
swapoff -a
- Step 2
- Comment out swap entries in
/etc/fstab:
proc /proc proc defaults 0 0
UUID=17e56a9a-0f42-44ca-90e8-570315708def / xfs relatime 0 1
# Swap entries commented out:
#UUID=0a403f5e-0505-4055-a219-70217b6b74d1 none swap sw 0 0
#UUID=4cf42564-4339-42ed-b7ec-29644a3085f1 none swap sw 0 0
- Step 3
- Monitor for OOM issues:
# Check for out-of-memory events
dmesg -T | grep -i "out of memory\|killed process"
Checking VoIPmonitor Memory Configuration
Before tuning system-level swap settings, review VoIPmonitor's internal memory configuration. Excessive buffer settings can cause memory pressure and trigger swap usage.
# Check current memory-related settings
grep -E '^(max_buffer_mem|ringbuffer|packetbuffer)' /etc/voipmonitor.conf
| Parameter | Default | Description |
|---|---|---|
ringbuffer |
50 MB | Ringbuffer size per interface. Recommended >= 500 for >100 Mbit traffic. Max 2000. |
max_buffer_mem |
2000 MB | Maximum buffer memory for packet buffers. |
packetbuffer_enable |
yes | Enable packet buffer cache. |
packetbuffer_compress |
no | Compress packet buffer (saves RAM, uses CPU). |
If your sensor is swapping, reduce ringbuffer and max_buffer_mem unless capturing at very high traffic rates.
See Sniffer Configuration for complete memory and buffer documentation.
Checking Current Memory and Swap Usage
# Check memory and swap status
free -m
# Monitor memory usage over time
watch -n 1 free -m
# Check which processes use most memory
ps aux --sort=-%mem | head -10
See Also
AI Summary for RAG
Summary: Linux swap configuration for VoIPmonitor servers. Covers swappiness tuning (recommended value 5), disabling swap completely, and VoIPmonitor buffer memory settings (ringbuffer, max_buffer_mem) that affect swap usage.
Keywords: swap, swappiness, memory, RAM, performance, ringbuffer, max_buffer_mem, OOM, out of memory, packetbuffer
Key Questions:
- How to configure swap for VoIPmonitor?
- How to disable swap on Linux?
- What is swappiness and how to configure it?
- How to reduce VoIPmonitor memory usage?
- What are ringbuffer and max_buffer_mem settings?