What are VPS memory ballooning and host overcommit?
Memory ballooning is a virtualisation mechanism that can adjust memory available to a guest. Host overcommit is a resource-allocation policy. Neither can be fully diagnosed from one free-memory figure inside the VPS, and the service’s memory guarantee remains the authoritative commitment.
Instructions
1. Check what the plan promises
Confirm the assigned memory amount, any minimum guarantee and whether dynamic memory is used. Do not assume every VPS provider enables the same overcommit or ballooning behaviour.
2. Inspect guest memory and symptoms
Read the Linux guest’s current view without changing memory or swap settings.
free -h
vmstat 1 5Review available memory, swap activity and runnable or blocked work. The first vmstat line can represent averages since boot; use the following interval samples for the current period.
3. Escalate with correlated evidence
Record the time, allocated RAM, guest-visible total, application symptoms and sustained pressure. The provider can check host allocation, balloon activity and contention. A guest command cannot force the host to honour a different resource allocation.
Check the result
- Guest-visible memory is compared with the service allocation and platform behaviour.
- Any performance claim is supported by application impact and time-correlated measurements.
Troubleshooting
- Used memory is high but applications are healthy
- File cache and other useful memory use can make a simple used figure misleading; review available memory and pressure.
- Assigned and visible memory differ materially
- Ask the provider to check the guest configuration and dynamic-memory policy before applying speculative tuning.
Official references
Use the documentation for your installed version when a flag, service name or platform feature differs.