VirtIO-FS DAX Support Close To Mainline For Offering Tremendous Performance Boost
Written by Michael Larabel in Linux Storage on 30 August 2020 at 10:37 AM EDT. 5 Comments
LINUX STORAGE --
Judging from the latest FUSE Git activity, it's looking like the VirtIO-FS DAX patches that have been around since last year could be merged for Linux 5.10. This can provide a significant speed-up for those making use of this FUSE file-system for sharing files/folders with guest VMs.

VirtIO-FS provides a means of file sharing between the host systems and guest VMs making use of VirtIO. VirtIO-FS relies on FUSE while an important performance feature that has been worked on is direct access (DAX) support.

VirtIO-FS with DAX can "improve performance for most of the operations in general a great deal." Besides needing these patches, there is also a "dax" mount option for enabling the direct access mode. Additionally, the support is toggleable at build time via a FUSE_DAX Kconfig switch. The speed-up comes by allowing the bypassing of the guest page cache and allowing the mapping of the host page cache directly in the guest address space.

There are some performance numbers showing the likes of sequential reads going from ~35 to ~245 MiB/s as well as write performance improving immensely.

The work was queued up two days agon FUSE.git's DAX branch and will hopefully see mainline with the Linux 5.10 merge window in October.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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