On 01/19/2018 06:50 AM, Anton Nefedov wrote: > A block driver can provide a callback to report driver-specific > statistics. > > file-posix driver now reports discard statistics > > Signed-off-by: Anton Nefedov <[email protected]> > Reviewed-by: Vladimir Sementsov-Ogievskiy <[email protected]> > ---
> +++ b/qapi/block-core.json
> @@ -774,6 +774,40 @@
> 'timed_stats': ['BlockDeviceTimedStats'] } }
>
> ##
> +# @BlockDriverStatsFile:
> +#
> +# File driver statistics
> +#
> +# @discard_nb_ok: The number of succeeded discard operations performed by
> +# the driver.
> +#
> +# @discard_nb_failed: The number of failed discard operations performed by
> +# the driver.
> +#
> +# @discard_bytes_ok: The number of bytes discarded by the driver.
> +#
> +# Since 2.12
> +##
> +{ 'struct': 'BlockDriverStatsFile',
> + 'data': {
> + 'discard_nb_ok': 'int',
> + 'discard_nb_failed': 'int',
> + 'discard_bytes_ok': 'int'
> + } }
New interfaces should prefer '-' over '_', where possible (a reason for
using '_' is if the fields are alongside pre-existing fields that
already used '_'). Let's see how this gets used...[1]
> +
> +##
> +# @BlockDriverStats:
> +#
> +# Statistics of a block driver (driver-specific)
> +#
> +# Since: 2.12
> +##
> +{ 'union': 'BlockDriverStats',
> + 'data': {
> + 'file': 'BlockDriverStatsFile'
> + } }
Markus has been adamant that we add no new "simple unions" (unions with
a 'discriminator' field) - because they are anything but simple in the
long run.
> +
> +##
> # @BlockStats:
> #
> # Statistics of a virtual block device or a block backing device.
> @@ -785,6 +819,8 @@
> #
> # @stats: A @BlockDeviceStats for the device.
> #
> +# @driver-stats: Optional driver-specific statistics. (Since 2.12)
> +#
> # @parent: This describes the file block device if it has one.
> # Contains recursively the statistics of the underlying
> # protocol (e.g. the host file for a qcow2 image). If there is
> @@ -798,6 +834,7 @@
> { 'struct': 'BlockStats',
> 'data': {'*device': 'str', '*node-name': 'str',
> 'stats': 'BlockDeviceStats',
> + '*driver-stats': 'BlockDriverStats',
...[1] You are using it alongside a struct that already uses '-'
(node-name), so you should use dashes.
So, the difference between your proposal (a simple union) and using a
"flat union", on the wire, is yours:
"return": { ..., "driver-stats": { "type": "file", "data": {
"discard_nb_ok: ... } } }
vs. a flat union:
"return": { ..., "driver-stats": { "driver": "file", "discard-nb-ok":
... } }
where you can benefit from less nesting and a saner discriminator name.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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