Windows 10 Fast Ringers – sorry, 'Dev Channel' – tossed Linux GPU support for WSL2 in latest Insider preview build

Also: Kernel updating and benchmarking the beast

After months of moribund emissions, Microsoft's loyal cadre of Fast Ring (or Dev Channel) Insiders were rewarded with toys aplenty last night as Windows 10 crested the build 20,000 mark.

Build 20150 was heavy on fixes and Windows Subsystem for Linux (WSL) tweaks. The latter received the promised GPU compute, a one-command install and the ability to manage the Linux kernel version.

Although the Linux desktop app support that Microsoft trumpeted at the recent virtual Build shindig remains missing for the time being, the arrival of GPU support will extend the usefulness of WSL into areas such as machine learning under Linux.

WSL also received a new command wsl --install to minimise installation fuss and wsl --update for managing the Linux kernel version. Rather than being part of the OS base image, the Linux kernel will be delivered via Windows Update but, in an acknowledgement that people just love to tinker, the command line option will allow a bit more control as well as the ability to rollback to the last used kernel.

Program manager Craig Loewen proclaimed the GPU support as "WSL's #1 most requested feature," which might raise an eyebrow among those encountering performance issues on the platform.

While the VM-happy WSL2 screams along at an impressive lick (certainly when compared to WSL1 and its translation layer), trying to access the Windows file system requires a hop over the VM boundary, which slows things to a crawl.

The issue has seen several developers, unable to remain solely in the Linux file system, trudge back to WSL1. Sven Groot, senior software engineer at Microsoft, explained the problem back in March and said the gang had been unable to deal with it in Windows 10 2004, but had improvements "in the pipeline."

It's a shame because otherwise the performance of WSL2 is impressive even without GPU support. The team at Phoronix carried out some benchmarking that pitted Ubuntu 20.04 running on WSL1, WSL2 and bare metal against each other.

When running in the Linux file system, there is just a gnat's whisker between Ubuntu 20.04 on bare metal and under WSL2. The former is faster by just 8 per cent over the benchmarks. The geometric mean of the benchmarks also showed WSL2 giving around 21 per cent better performance over its predecessor.

As for the new build itself, the raft of fixes include one to deal with the resource monitor showing CPU usage at more than 100 per cent as well as Visual Studio windows not consistently accepting clicks.

Microsoft also warned that some systems might fall over with a HYPERVISOR_ERROR bugcheck and that Notepad fans should beware: the beloved text editor might not reopen files that were automatically saved during a PC upgrade or restart (although the text can still be recovered). ®