Re: [PATCH v5 0/7] fuse: {io-uring} Allow to reduce the number of queues and request distribution

On 2026-05-28 15:55, Bernd Schubert via B4 Relay wrote:
> This adds bitmaps that track which queues are registered and which queues
> do not have queued requests.
> These bitmaps are then used to map from request core to queue
> and also allow load distribution. NUMA affinity is handled and
> fuse client/server protocol does not need changes, all is handled
> in fuse client internally.
> 
> Signed-off-by: Bernd Schubert <[email protected]>
> ---
> Changes in v5
> - Rebased to miklos-for-next (Linux 7.2 base).
> - Folded "Fetch a queued fuse request on command registration" into
>    "Allow reduced number of ring queues", inlining fuse_uring_do_register()
>    into fuse_uring_register().
>    - Fixed retry logic in "Add retry attempts for numa local queues":
>      replaced cpu++ with cpumask_next_wrap(qid, mask) so each retry
>      advances to a genuinely different registered queue (Joanne)-
>    - Simplified "Prefer the current core over mapping" (Joanne).
>    - Folded READ_ONCE() annotation for ring->ready into "Allow reduced
>      number of ring queues" to match WRITE_ONCE() on the writer side and
>      suppress a KCSAN data-race warning.
> 
> Changes in v4:
> - Fix leak of ring->numa_q_map
> - Fix q-imbalance due to an issue in static cpu->qid mapping
> - Performance tunings, like preferring the current cpu
> - Removal of distribution among queues, Joanne had concerns about it.
>    As it is an optimization, it can be added later again. At least
>    most of it was removed, some light distribution is still left in.
> - At the end of the series, add fuse debugfs entries. This could
>    be factored out.
> - Link to v3: https://lore.kernel.org/r/[email protected]
> 
> ---
> Bernd Schubert (7):
>        fuse: {io-uring} Add queue length counters
>        fuse: {io-uring} Rename ring->nr_queues to max_nr_queues
>        fuse: {io-uring} Use bitmaps to track registered queues
>        fuse: {io-uring} Allow reduced number of ring queues
>        fuse: {io-uring} Queue background requests on a different core
>        fuse: {io-uring} Add retry attempts for numa local queues for load distribution
>        fuse: {io-uring} Prefer the current core over mapping
> 
>   fs/fuse/dev_uring.c       | 313 ++++++++++++++++++++++++++++++++++------------
>   fs/fuse/dev_uring_i.h     |  25 +++-
>   fs/fuse/inode.c           |   2 +-
>   include/uapi/linux/fuse.h |  10 +-
>   4 files changed, 269 insertions(+), 81 deletions(-)
> ---
> base-commit: 2dcf16d41cc04472a4f9bc6e99d0ab26cfb1afb1
> change-id: 20250722-reduced-nr-ring-queues_3-6acb79dad978
> 
> Best regards,

Hi Bernd,

What is the current status of this patchset? Do you intend to keep it as
is, or as Joanne mentioned combine it with queue add/remove?

We're running FUSE io_uring on fairly large hosts with >150 physical
cores. FUSE io_uring ends up creating 300+ io_uring instances, which
wastes memory and bumps against rlimit memlock.

Thanks,
David