firecracker-microvm/firecracker

Unmap/discard/fstrim

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#2,708 opened on Aug 24, 2021

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 (12 comments) (5 reactions) (0 assignees)Rust (34,348 stars) (2,393 forks)batch import
Good first issuePriority: MediumRoadmap: New RequestStatus: Parked

Description

Is firecracker supporting unmap/discard/fstrim, ie automatic reduction of the image size on the host when a file is deleted on the guest? If it does how do I enable it?

Contributor guide

Tech stack
rust
Domain
backendperformance
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
RustFirecracker architecturevirtio blk
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
Examine the Firecracker codebase, specifically the virtio blk device implementation (e.g., src/vmm/src/devices/virtio/block.rs). Review the Linux kernel documentation on fstrim and discard operations. Check the issue comments for any maintainer feedback on feasibility or design considerations. Investigate how other VMMs (e.g., QEMU) implement discard support for reference.