When Microsoft announced that DirectStorage — the next gen storage feature for gaming — would come to Windows 10 (build 1909 and up), they stated that it would perform better on Windows 11 due to its new and improved storage stack. Until recently, Microsoft has provided no details on what that would entail. However, they have now released documentation to the public about a new API called I/O rings, which you can read here in full. Here is how Microsoft describes this new API:
I/O rings maintain a submission queue of I/O operations to be performed asynchronously and a completion queue containing the results of the completed operations.
In other words, this will allow Windows, or third party applications using this feature, to submit batch I/O requests, as opposed to serialized requests, as has been the case until now. This will allow advanced storage devices, such as NVMe SSDs, to achieve their full bandwidth potential.
Furthermore, a couple of functions which register an array of buffers for future I/O ring operations, and register an array of file handles — BuildIoRingRegisterBuffers and BuildIoRingRegisterFileHandles, respectively — were designed to reduce overhead. Both of these functions allow the kernel implementation to perform the validation and internal mapping just once, avoiding the overhead on each I/O operation.
Creating an instance of an I/O ring is done with the CreateIoRing function, using the following parameters:
ioringVersion: UNIT32 which represents the version of the I/O ring API the ring was created for.
flags: creation flags from the IORING_CREATE_FLAGS enumeration.
submissionQueueSize: the requested minimum submission queue size.
completionQueueSize: the requested minimum size of the completion queue.
h: HIORING handle, if created successfully.
For each function and data structure used in the API, the minimum supported Windows build is listed as 22000, which means that this API will indeed be Windows 11 exclusive. It looks like, contrary to the belief of some, Windows 11 is more than just a cosmetic update. This new storage stack will allow the operating system, as well as third party applications, to finally take advantage of fast storage, and we should see an uptick in system and app responsiveness once it gets implemented.
By reading the documentation, it looks like DirectStorage will rely heavily on this new API. Which begs the question — how will it perform on Windows 10 with an antiquated storage architecture?
We will have extensive benchmarks of DirectStorage once games add support for it. Make sure to follow us here, as well as on social media, to see how DirectStorage will perform in practice. We will have plenty of videos on our YouTube channel.
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