Microsoft shipped a kernel update for WSL 2 in May 2026 that assigns each virtio device its own dedicated DMA pool, eliminating the last major contention point on the virtiofs path. The change lives in kernel 6.18.26.3‑1 and is activated when the WSL service reads per‑device swiotlb values from sysfs. Developers who cross the Windows‑Linux boundary will notice the effect immediately for development tasks today.

Earlier releases moved cross‑OS file access from DrvFs in WSL 1 to a Plan 9 9P server in WSL 2, then to an experimental virtiofs transport in 2021. Virtiofs reduced serialization overhead by sharing memory directly over the VirtIO channel, but all devices still contended for a single SWIOTLB buffer. The new per‑device allocation frees drives and the VirtioProxy network adapter from that bottleneck.

To reap the gains, users must enable virtiofs=true in their .wslconfig, run wsl.exe --update --pre‑release, and allocate at least 1 GB RAM so the SWIOTLB pool retains a 64 MB headroom. Opt‑in remains required; Plan 9 continues as the default transport. The per‑device DMA pool upgrade narrows the performance gap between Windows‑hosted files and native Linux workloads. This change also benefits container workloads inside WSL.