Re: [PATCH V5 13/13] qapi: examine IOThread attachment status via query-iothreads

[Markus Armbruster <armbru@redhat.com>]

Zhang Chen <zhangckid@gmail.com> writes:

> Extend the 'IOThreadInfo' structure to include attachment metrics.
> This allows users to monitor the associated devices by identify them
> by their QOM paths.
>
> New fields added to IOThreadInfo:
> - @holders: A string containing of QOM paths for the attached devices.
>
> These fields are also exposed via the Human Monitor Interface (HMP)
> command 'info iothreads' to assist with manual debugging and
> performance tuning.
>
> Signed-off-by: Zhang Chen <zhangckid@gmail.com>

[...]

> diff --git a/qapi/misc.json b/qapi/misc.json
> index 1f5062df2a..a381074c04 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -76,6 +76,15 @@
>  #
>  # @thread-id: ID of the underlying host thread
>  #
> +# @holders: The parameter is an array of QOM paths indicating how many
> +#     active devices are currently associated with this iothread
> +#     (e.g. virtio-blk).  In hotplug scenarios, users can
> +#     pre-allocate multiple iothread objects to serve as a persistent
> +#     thread pool.  When a device is hot-unplugged, the corresponding
> +#     IOThread is released but remains available, allowing subsequent
> +#     hot-plugged devices to attach to and reuse the existing thread.
> +#     Returns empty if no devices are attached.  (since 11.0)

Let me try to polish this a bit:

   # @holders: QOM paths of the devices currently associated with this
   #     iothread.  Users can pre-allocate multiple iothread objects to
   #     serve as a persistent thread pool.  When a device is
   #     hot-unplugged, it is detached from its iothread, but the
   #     iothread remains available, allowing future hot-plugged devices
   #     to attach to it.

> +#
>  # @poll-max-ns: maximum polling time in ns, 0 means polling is
>  #     disabled (since 2.9)
>  #
> @@ -93,6 +102,7 @@
>  { 'struct': 'IOThreadInfo',
>    'data': {'id': 'str',
>             'thread-id': 'int',
> +           'holders': ['str'],
>             'poll-max-ns': 'int',
>             'poll-grow': 'int',
>             'poll-shrink': 'int',
> @@ -118,6 +128,8 @@
>  #              {
>  #                 "id":"iothread0",
>  #                 "thread-id":3134,
> +#                 "holders":["/machine/peripheral/blk1/virtio-backend",
> +#                            "/machine/peripheral/blk0/virtio-backend"],
>  #                 "poll-max-ns":32768,
>  #                 "poll-grow":0,
>  #                 "poll-shrink":0,
> @@ -126,6 +138,7 @@
>  #              {
>  #                 "id":"iothread1",
>  #                 "thread-id":3135,
> +#                 "holders":["/machine/peripheral/blk2/virtio-backend"],
>  #                 "poll-max-ns":32768,
>  #                 "poll-grow":0,
>  #                 "poll-shrink":0,

With a bit of doc polish:
Acked-by: Markus Armbruster <armbru@redhat.com>