Re: [PATCH v1 03/11] io_uring/kbuf: add support for kernel-managed buffer rings

[Joanne Koong <joannelkoong@gmail.com>]

On Fri, Feb 27, 2026 at 12:05 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> On 2/24/26 22:19, Joanne Koong wrote:
> > On Mon, Feb 23, 2026 at 12:00 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
> >>
> >> On 2/21/26 02:14, Joanne Koong wrote:
> >>> On Fri, Feb 20, 2026 at 4:53 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
> >> ...
> >>>> So I'm asking whether you expect that a server or other user space
> >>>> program should be able to issue a READ_OP_RECV, READ_OP_READ or any
> >>>> other similar request, which would consume buffers/entries from the
> >>>> km ring without any fuse kernel code involved? Do you have some
> >>>> use case for that in mind?
> >>>
> >>> Thanks for clarifying your question. Yes, this would be a useful
> >>> optimization in the future for fuse servers with certain workload
> >>> characteristics (eg network-backed servers with high concurrency and
> >>> unpredictable latencies). I don't think the concept of kmbufrings is
> >>> exclusively fuse-specific though (for example, Christoph's use case
> >>> being a recent instance);
> >>
> >> Sorry, I don't see relevance b/w km rings and what Christoph wants.
> >> I explained why in some sub-thread, but maybe someone can tell
> >> what I'm missing.
> >>
> >>> I think other subsystems/users that'll use
> >>> kmbuf rings would also generically find it useful to have the option
> >>> of READ_OP_RECV/READ_OP_READ operating directly on the ring.
> >>
> >> Yep, it could be, potentially, it's just the patchset doesn't plumb
> >> it to other requests and uses it within fuse. It's just cases like
> >
> > This patchset just represents the most basic foundation. The
> > optimization patches (eg incremental buffer consumption, plumbing it
> > to other io-uring requests, etc) were to be follow-up patchsets that
> > would be on top of this.
>
> Got it. Any understanding how the work flow would look like if used
> with non-cmd io_uring requests? Is there some particular use case
> you have in mind for fuse servers?

One use case is for network-backed servers with high concurrency and
unpredictable latencies where with kmbuf rings we can submit multipel
recvs and have the buffer assignment be done as the completion comes
in rather than having to preassign the buffers before submission when
we don't know which requests will complete first.

Thanks,
Joanne