Re: [PATCH for-next v3 0/7] io_uring: defer task work to when it is needed

[Hao Xu <hao.xu@linux.dev>]

On 8/19/22 20:19, Dylan Yudaken wrote:
> We have seen workloads which suffer due to the way task work is currently
> scheduled. This scheduling can cause non-trivial tasks to run interrupting
> useful work on the workload. For example in network servers, a large async
> recv may run, calling memcpy on a large packet, interrupting a send. Which
> would add latency.
> 
> This series adds an option to defer async work until user space calls
> io_uring_enter with the GETEVENTS flag. This allows the workload to choose
> when to schedule async work and have finer control (at the expense of
> complexity of managing this) of scheduling.
> 
> Patches 1,2 are prep patches
> Patch 3 changes io_uring_enter to not pre-run task work
> Patch 4/5/6 adds the new flag and functionality
> Patch 7 adds tracing for the local task work running
> 
> Changes since v2:
>   - add a patch to trace local task work run
>   - return -EEXIST if calling from the wrong task
>   - properly handle shutting down due to an exec
>   - remove 'all' parameter from io_run_task_work_ctx
>   
> Changes since v1:
>   - Removed the first patch (using ctx variable) which was broken
>   - Require IORING_SETUP_SINGLE_ISSUER and make sure waiter task
>     is the same as the submitter task
>   - Just don't run task work at the start of io_uring_enter (Pavel's
>     suggestion)
>   - Remove io_move_task_work_from_local
>   - Fix locking bugs
> 
> Dylan Yudaken (7):
>    io_uring: remove unnecessary variable
>    io_uring: introduce io_has_work
>    io_uring: do not run task work at the start of io_uring_enter
>    io_uring: add IORING_SETUP_DEFER_TASKRUN
>    io_uring: move io_eventfd_put
>    io_uring: signal registered eventfd to process deferred task work
>    io_uring: trace local task work run
> 
>   include/linux/io_uring_types.h  |   3 +
>   include/trace/events/io_uring.h |  29 ++++
>   include/uapi/linux/io_uring.h   |   7 +
>   io_uring/cancel.c               |   2 +-
>   io_uring/io_uring.c             | 264 ++++++++++++++++++++++++++------
>   io_uring/io_uring.h             |  29 +++-
>   io_uring/rsrc.c                 |   2 +-
>   7 files changed, 285 insertions(+), 51 deletions(-)
> 
> 
> base-commit: 5993000dc6b31b927403cee65fbc5f9f070fa3e4
> prerequisite-patch-id: cb1d024945aa728d09a131156140a33d30bc268b

Apart from the comments, others looks good to me,

Acked-by: Hao Xu <howeyxu@tencent.com>