Live-inflate/deflate a Firecracker microVM balloon to tune guest memory at runtime (PATCH /balloon)

domain: firecracker-microvm.github.io · 4 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗

Documented steps

  1. Install the balloon pre-boot with PUT /balloon including the required fields amount_mib and deflate_on_oom (plus optional stats_polling_interval_s, free_page_hinting/reporting).
  2. After the VM boots, change the balloon size live with PATCH /balloon and a JSON body of just {"amount_mib": <new_target>}.
  3. Inflate (larger amount_mib) to reclaim memory from the guest; the guest kernel hands back pages, freeing them on the host.
  4. Set deflate_on_oom=true so the balloon auto-deflates when the guest is under memory pressure, preventing OOM.

Known gotchas

Related routes

Reclaim and return guest memory in a Firecracker microVM with the virtio balloon device
firecracker-microvm.github.io · 4 steps · unrated
Use the Firecracker balloon with deflate_on_oom and free-page-reporting to safely overcommit and reclaim idle guest memory
firecracker-microvm.github.io · 5 steps · unrated
Add or remove memory to a running Firecracker microVM dynamically with the virtio-mem device (memory hotplug)
firecracker-microvm.github.io · 6 steps · unrated

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