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Huge Pages Requirement Calculator

Work out huge pages requirement instantly with clear inputs, formula shown and shareable results.

About Huge Pages Requirement Calculator

Huge pages reduce TLB pressure by mapping 2 MB or 1 GB per entry instead of 4 KB, which measurably improves performance for large-memory databases and JVMs. The cost is that reserved huge pages are unavailable to anything else, even when idle, so over-reserving starves the rest of the system.

Formula

Huge page reservation

pages = ceil(memory x (1 + overhead) / page size); reserved = pages x page size; 4 KB entries avoided = memory / 4 KB - pages

Worked example

With the default values below, Huge Pages Requirement Calculator returns Huge pages to reserve of 25,805. Change any input above and every figure here is recalculated in your browser.

Inputs used

Memory to back with huge pagesminimum 0.001 GB
48 GB
Huge page sizeone of 2 MB, 1 GB
2 MB
Allocation overhead allowanceaccepts 0–50 %
5 %
Total system RAMminimum 0.1 GB
128 GB

Results

Huge pages to reserve
25,805
Memory reserved
50.40 GB
RAM left for everything else
77.60 GB
Page table entries avoided
12,557,107

Step by step

  1. 1Values used
  2. 2Huge page reservation
  3. 3Huge pages to reserve= 25,805
  4. 4Memory reserved= 50.40 GB
  5. 5RAM left for everything else= 77.60 GB
  6. 6Page table entries avoided= 12,557,107

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 transparent huge pages be used instead?

For databases, usually not. THP's background defragmentation causes latency spikes, which is why PostgreSQL, MongoDB and Redis all recommend disabling it in favour of explicit reservations.

Why reserve at boot?

Because contiguous physical memory fragments over time. Reserving 1 GB pages after the system has been running often fails outright.

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