# Experimental synchronous queues cut VirtIO-FS build times by 28%

> **Key takeaway:** Pending synchronous queue support for VirtIO-FS reduced a libkrunfw build from 7:43 to 5:34 and improved random I/O and file deletion latency.

**Published:** 2026-10-18T00:55:35+00:00 
**Source:** Phoronix Linux Gaming & Graphics Drivers 
**Category:** open-gaming 
**Canonical URL:** https://fosswire.org/news/experimental-synchronous-queues-cut-virtio-fs-build-times-by.html 

## Summary
Sergio López has developed experimental synchronous queue support for VirtIO-FS, the paravirtualized file system used for host-guest VM data transfers. Unlike VirtIO's typical asynchronous model, synchronous queues let the host vCPU thread complete I/O requests before returning to the guest. A libkrunfw build test showed a 28% time reduction, with additional gains in random I/O and file deletion performance. The work is available as a pending pull request for libkrun adding optional VIRTIO_FS_F_SYNC support.

## How synchronous queues change VirtIO-FS behavior
- **Default VirtIO model**: asynchronous queues where the guest continues execution without waiting for I/O completion
- **Synchronous approach**: host vCPU thread blocks and completes the request before returning to guest context
- **Measured workload**: libkrunfw build time dropped from **7:43 to 5:34** (approximately 28% faster)
- **Additional gains**: significant random I/O improvement and lower file deletion latency
- **Implementation status**: experimental pull request for libkrun with optional `VIRTIO_FS_F_SYNC` flag

## Why it matters
If merged, this could improve VM-based development and CI workloads that rely on VirtIO-FS for shared host-guest storage, particularly for build-heavy and metadata-intensive operations.