Swappiness Effect Calculator

Work out swappiness effect instantly with clear inputs, formula shown and shareable results.

About Swappiness Effect Calculator

vm.swappiness balances reclaim between anonymous process memory and page cache, on a scale where 0 strongly prefers dropping cache and 100 treats them equally — values above 100 favour swapping. It is not an on/off switch: even at 0 the kernel will swap rather than invoke the OOM killer. Latency-sensitive databases typically set it to 1 or 10.

Formula

Swappiness balance

anonymous reclaim share ~ swappiness / 200; page cache share = 1 - that; swappiness 0 still permits swap under real pressure

Worked example

With the default values below, Swappiness Effect Calculator returns Reclaim pressure applied to process memory of 30.0%. Change any input above and every figure here is recalculated in your browser.

Inputs used

vm.swappiness valueaccepts 0–200: 60
Total RAMminimum 0.1 GB: 32 GB
Anonymous (process) memoryminimum 0 GB: 24 GB
Swap device latencyminimum 1 us: 120 us

Results

Reclaim pressure applied to process memory: 30.0%
Reclaim pressure applied to page cache: 70.0%
Process memory eligible for swapping: 7.20 GB
Latency penalty: Each swapped page costs about 120 microseconds to fault back in, against roughly 0.1 for a RAM access

Step by step

1Values used
2Swappiness balance
3Reclaim pressure applied to process memory= 30.0
4Reclaim pressure applied to page cache= 70.0
5Process memory eligible for swapping= 7.20 GB
6Latency penalty= Each swapped page costs about 120 microseconds to fault back in, against roughly 0.1 for a RAM access

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Should swappiness be 0?

It reduces swapping but does not prevent it, and it increases the chance of the OOM killer firing. A value of 1 to 10 is the usual recommendation for databases.

Why is high swappiness sometimes better?

On systems with idle memory-hungry processes and a heavy file workload, swapping out cold anonymous pages to keep more cache resident genuinely improves throughput.