New storage features, especially in NVMe, are emerging fast. It
takes time and a good deal of consensus-building for a device-feature
to move up the ladders of kernel I/O stack and show-up to user-space.
This presents challenges for early technology adopters.
The passthrough interface allows such features to be usable (at least
in native way) without having to build block-generic commands,
in-kernel users, emulations and file-generic user-interfaces. That said,
even though passthrough interface cuts through layers of
abstraction and reaches to NVMe fast, it has remained tied to
synchronous ioctl interface, making it virtually useless for fast I/O path.
In this talk I will present the elements towards building a scalable
passthrough that can be readily used to play with new NVMe features.
More specifically, recent upstream efforts involving:
- Emergence of per-namespace char interface, that remains
available/usable even for unsupported features and new command-sets
- Async-ioctl facility 'uring_cmd' that Jens proposed in io_uring .
- Async nvme-passthrough that I put up over 'uring_cmd' 
Performance evaluation comparing this new interface with existing ones
will be provided.
I would like to gather the feedback on the design-decisions, and discuss
how best to go about infusing more perf-centric advancements (e.g.
async polling, register-buffer etc.) into this path.
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