Re: [PATCH RFC v7 00/16] fuse: fuse-over-io-uring

[Pavel Begunkov <asml.silence@gmail.com>]

On 11/27/24 13:40, Bernd Schubert wrote:
> [I removed RFC status as the design should be in place now
> and as xfstests pass. I still reviewing patches myself, though
> and also repeatings tests with different queue sizes.]

I left a few comments, but it looks sane. At least on the io_uring
side nothing weird caught my eye. Cancellations might be a bit
worrisome as usual, so would be nice to give it a good run with
sanitizers.

> This adds support for uring communication between kernel and
> userspace daemon using opcode the IORING_OP_URING_CMD. The basic
> approach was taken from ublk.
> 
> Motivation for these patches is all to increase fuse performance,
> by:
> - Reducing kernel/userspace context switches
>      - Part of that is given by the ring ring - handling multiple
>        requests on either side of kernel/userspace without the need
>        to switch per request
>      - Part of that is FUSE_URING_REQ_COMMIT_AND_FETCH, i.e. submitting
>        the result of a request and fetching the next fuse request
>        in one step. In contrary to legacy read/write to /dev/fuse
> - Core and numa affinity - one ring per core, which allows to
>    avoid cpu core context switches
> 
> A more detailed motivation description can be found in the
> introction of previous patch series
> https://lore.kernel.org/r/20241016-fuse-uring-for-6-10-rfc4-v4-0-9739c753666e@ddn.com
> That description also includes benchmark results with RFCv1.
> Performance with the current series needs to be tested, but will
> be lower, as several optimization patches are missing, like
> wake-up on the same core. These optimizations will be submitted
> after merging the main changes.
-- 
Pavel Begunkov